Tips on Troubleshooting Your Home Thermostat

by on December 2, 2012Karie Fay

thermostat troubleshootingBefore assuming your furnace is broken, remember that you could have a malfunctioning thermostat. From heating and cooling systems that seem to have failed to those that overwork – heating or cooling more than the temperature settings dictate – a thermostat throwing fits can masquerade as an appliance problem.

Before calling out expensive HVAC repair companies, try troubleshooting your thermostat first. In many instances, simply repairing the thermostat or replacing it with a new one will save on unnecessary service calls.

Thermostat Basics

How the thermostat senses the temperature and how it responds varies according to the type – electromechanical or electronic.

Electromechanical Thermostats:

  • Considered somewhat old-fashioned, electromechanical thermostats operate on basic mechanical principles. A bimetallic strip – a fancy name for what is nothing more than joined pieces of two different metals – rests, sometimes in a coil, under the thermostat cover. As the room temperature fluctuates, the coil expands or contracts, activating the contact. Think of a contact as a light switch – when flipped, an electrical circuit closes and the light – or the furnace or central air, in this case – operates. Without the contact, the electrical circuit is open and nothing happens.
  • Sometimes, the bimetallic switch is coupled with a mercury switch – a small glass tube or “ampoule” filled with mercury – that tilts as the coil expands or contracts. A liquid conductor of electricity, as the mercury moves from one side of the tube to the other it either closes or opens the contact.
  • If the thermostat controls both a heating and air unit, it has contacts on both sides. The mercury or bimetallic switch tilts in one direction for heat and the opposite for cooling. As the temperatures fluctuate, contact is made or broken and the circuit opened or closed on the given side, activating the corresponding equipment.

Electronic Thermostats:

  • Instead of mercury-filled tubes and strips of metal, electronic thermostats use heat-sensing receptors to monitor the room temperature and electrical circuits to respond to the digital data, turning on or off your heating and cooling equipment. Similar to a small computer, electronic thermostats will store data, allowing you to program settings. Wake up to a warm house, cool it while you sleep and set it to different temperatures on weekends to correspond to your needs. All it takes is a few pushes of the buttons.
  • Digital sensors and circuitry provide greater temperature accuracy. Bimetallic strips and mercury switches allow “deadband” – a temperature range between which it fails to activate or shut down the furnace or air. This means even if you set your thermostat to 70 degrees Fahrenheit, the switch may not activate to turn equipment on or off until it’s much lower or higher.
  • Thermostats may wear out. Since electronic thermostats involve electronic equipment instead of purely mechanical components, these thermostats are more complex, meaning there are more things to wear out. Consult the manufacturer’s thermostat literature or contact a qualified technician for troubleshooting specific to the thermostat involved. Given the relatively low replacement cost, in many cases buying and installing a new thermostat may prove a more cost-effective option.

Common Thermostat Problems

Most thermostat failures aren’t dramatic. Chances are, no shooting sparks, puffs of smoke or piercing alarms will signal you have a problem. It may be obvious, like the furnace refuses to come on or the display isn’t lit, or you may notice that the house is cooler than the temperature setting. All you know is something’s wrong and you want it fixed. Always start with the thermometer, troubleshooting according to the symptom. Many symptoms and causes overlap, and the general solutions narrow down to one of a handful of fixes.

Furnace or Central Air Doesn’t Start:

  • Check for power. A blown fuse, tripped circuit breaker or dead batteries will prevent the thermostat from turning on the appliance.
  • Is the thermostat excessively dirty? Buildup of dust, dirt, spiderwebs and nicotine, for example, can coat the inside of the thermostat, interfering with both electrical and mechanical components. It’s easy to overlook the inside of your thermostat during spring-cleaning, so a dirty thermostat is nothing uncommon. Simply use a soft, clean brush – an artist’s paintbrush works well – to brush the interior components gently. Move parts to ensure you reach every portion of the thermostat.  A can of compressed air, such as is used for electronics, also works well.
  • Are there loose wires or terminal screws inside the thermostat? Are the wires corroded? Never remove the thermostat cover without removing the batteries or cutting the power at the fuse or breaker box. Tighten screws and secure loose wires when necessary. Consult the manufacturer’s wiring schematics or have a qualified technician rewire the thermostat if needed.
  • Replace the thermostat if other troubleshooting methods fail. The most expensive programmable electronic thermostat costs around a couple hundred dollars, and inexpensive mechanical ones cost around $20. Worrying over a thermostat you can’t make work – or paying a professional more than a new one costs – just isn’t worth it.

 The Room Temperature Doesn’t Match the Thermostat Setting:

  • Is the inside of the thermostat clean? A dirty thermostat is an inaccurate thermostat.
  • Is the thermostat level? Hold a level underneath or above it and check. Careless installation or a forceful bump, knocking it off level, may alter the accuracy of the components.
  • Is the thermostat in a poorly chosen area of the home? Thermostats located in direct sunlight, in front of cold or drafty windows and doors, or isolated from the main living areas may not regulate the temperature correctly. Consider relocating the thermostat, if possible, or taking other measures to solve the problem. Consult a professional for further information.
  • The anticipator may not be set correctly. The anticipator is a little metal tab inside mechanical thermostats, mounted to a round dial with a printed scale. Pushing lightly on the anticipator, in either direction, may solve the issue. More complex adjustments require moving the anticipator to indicate the ampere setting needed for the furnace involved. Typically, this is specified in the owner’s manual or on the unit’s service panel. Consult a qualified technician for further assistance.

The Unit Turns On and Off Constantly or Won’t Turn Off:

  • Is the thermostat clean, inside and out? Buildup of any type may interfere with proper thermostat operation.
  • Does the anticipator need adjustment? Simply moving the anticipator arm one notch toward longer should cause a furnace to run longer during its cycle. Moving it away helps if the room temperature fails to reach the thermostat settings. Wait two or three hours after any adjustments to see if the problem is solved.
  • Is the thermostat completely level? Use a level to adjust it until correct.

Updating Your Thermostat

If all else fails, consider completely replacing your old thermostat with a new digital, electronic thermostat. With a wide range of features and price tags, there’s one to fit most any budget. Touch screen operation, digital displays, alarms to remind you when it’s time to change your HVAC filters and other options make these thermometers very convenient.

Better yet, electronic thermostats help you save money. With old thermostats, every adjustment requires your attention. Programmable electronic thermostats, in contrast, allow you to maintain settings, letting you heat or cool your home only when you need it. The Department of Energy estimates you can save about 10 percent on your heating and cooling bill merely by lowering your thermostat 7 to 10 degrees for eight hours a day during the heating season and raising it similarly during the cooling season. When you think about it, that’s enough savings to pay your utility bill for almost an entire month.

Installing an electronic thermostat is, however, more complicated than installing a mechanical one due to the programming needed. An improperly installed thermostat can, of course, cause significant problems. If you are uncertain about your ability to install or program your own, contact a specialist to do it for you.

{ 138 comments… read them below or add one }

Jerry Kantor November 24, 2014 at 7:51 am

We have a bizarre situation with our Honeywell digital thermostat. Whenever we are running our wood fireplace the house furnace kicks in and thermostat says it’s 63° in the house even though it feels warmer. So I set it to 60° to get the furnace to shut it off but after about 15 minutes the thermostat reads 59° and kicks in again even though it feels comfortable. Finally, at setting of 55° it stays off. So, in the middle of the night the house gets really cold. When we don’t run the fireplace the automatic settings work perfectly. I can’t think of any explanation to this psychic phenomenon. (The wall temperature of the thermostat feels normal.)


malcolm November 20, 2014 at 11:16 pm

Why is it when i wake up my house is so cold. Should not the thermostat comes on automactically?


Jason Berry November 20, 2014 at 3:57 am

Good day every one, (I guess all considering) .. I have question if anyone can help me out with a simple yes or no please, I was wondering if a thermostat will cause a home furnace to almost constantly run but while running only at times will make the furnace kick on the correct way (meaning to actually produce the heat to turn on) , I’ve had the mother board on my furnace replaced last year and have bad everything check at this time. Now this year when the furnace comes on it only produces heat to come on for a few minutes. But the blower will continue to blow cool air once the flames go out , causing the cooler air. So to make this a little shorter will a digital thermostat cause this to happen beings I’ve already had technically everything else replaced or fixed on the furnace itself? If anyone knows if this could be the reason please email me back at , thank you for your time and answers to this question.


Trudy H November 18, 2014 at 1:55 pm

Everything has been running fine for a month. Woke up today and was down to 64 when it was set to 74. It never gets up to temp. We have cleaned everything, restarted it but just doesn’t warm the house. Its finally up to 70′ but I had to set it to 80 to do so. Why is it registering 10′ below setting???


mandy November 21, 2014 at 1:56 pm

I have the same problem. I have mine at 90 now, just so the temp can sit at 71 in my house and it still feels like its set at about 55-60.


Vicky Brown November 17, 2014 at 4:27 am

Heating in home notheating blowing only cool air .
Reaches77° and shuts off what causes this?


Teresa November 14, 2014 at 11:37 pm

my old thermostat came on and off at its own pleasure no matter how it was set on the thermostat. Installed new Honeywell, and it still does what it wants on at 53 or so off at 63 or so, no matter what I set it to, HOW DO I FIX THIS


Eunice Shumalski November 22, 2014 at 11:54 am

I have the same problem even though I also had a new thermostat installed. How to correct this?


Patti November 14, 2014 at 8:13 am

We did but a new thermostat a programmable one and cannot get the furnace to keep the temperature ( which is why we bought a new one) We have it set on 80 and it goes to 67 and shuts off it does drop to 65 before kicking back on.


Cheri B November 13, 2014 at 8:20 pm

We have been away from our home for a month. When we left I turned both thermostats off. But on our recent electric bill I noticed increasing spikes in our use age (we have gas heat). When I called the electric company to ask for an inspection they said that the furnace will still operate. Is this true and how can that be possible?


Faith November 13, 2014 at 5:49 pm

HI, hoping you can provide some insights. I bought a home (first cold months here) and the furnace seems to run nonstop and the temp in the house seems hotter than the temp on the thermostat. I got up 3 x last night burning up and if I leave the house and leave it at a low temp to conserve energy say 66 degrees with noone here, I walk in the front door and heat feels much hotter and just hits you. The AC on it works fine so why did the furnace run non stop all night? It appears the thermostat is not shutting the furnace down when it reaches designated temperature. Thanks! Faith


Angela Corrado November 8, 2014 at 3:51 pm

Hi hope you can help. My thermostate read 66 degrees and I push it up to 68 degrees and the heat wont go on Then I raise the heat up to 72 then the heat goes on. What does this mean.


laura November 19, 2014 at 9:35 am

Hi, Angela. I’m just a lady homeowner, but my experience is that your thermostat may have a setting for a temperature difference at which to come on. Example: My thermostat has a 2 degree temperature difference set, so in the summer it will come on when the temp is 2 degrees higher than what I want and in the winter it will come on when the temp is 2 degrees lower than what I want. To see how you can adjust this difference, you will need to consult the owners manual that came with your thermostat. If you do not have one, look for it online. You will need the information from the back/inside of your thermostat to get the proper manual. Hope this helps!


Sandy November 19, 2014 at 8:51 pm

That is something. I wil look at. As a new home ower I see my thermastat showing a one I r two figit diff. Thanks for the info.


Raymond Landeros November 20, 2014 at 3:55 pm

I have the same problem.


Dino Anastos November 4, 2014 at 7:05 pm

I have a basic Honeywell round heat only thermostat. The house has baseboard heat (water not electric). When the inside temp is 70. I have to set the desired temp to 80 before it calls for heat and it won’t shut off until I turn it back to 60. I already replaced the outer part of the thermostat. Any ideas? I am also uncertain how to set the switches as far as the cph it should have. Help!!!!


yanira November 4, 2014 at 12:40 pm

my furnace heat works and fan works but when it reaches the desire temperature shuts off (like it should since is set in auto) but it wont come back as the temperature drops.
If i raise the temperature it still not comes on unless we go the fuse box and take out the fuse to reset it.
thanks in advance for your reply


Teresa October 31, 2014 at 10:38 pm

Our furnace runs when it wants not in relation to the temp the thermostat is set . I Tried turning the thermostat to 90 to get it to come on as it was cold. NO response. It went on as I pushed it up more. A hour or so later, it came on ran and maybe got to 70 in here, with thermostat still way up. IT continues to run periodically but not according to the set temp PLEASE HELP


Gary October 24, 2014 at 7:05 am

I had a 5 hour power outage and since then I had problems. It is a programmable thermostat that reads 20 C degrees all the time. I can override it (higher) and it adjust. I can program it but within a day it goes back to the default preprogram. I changed the thermostat but the ambient temperature reads 20 C and never seems to drop at night although the programmed temperature shows on the thermostat.


Steven October 17, 2014 at 11:23 pm

Hi, i have a fuji pxr controller,when i set it at 70 degree c it will cut off,but the reading give on goes up till 90 something then it start to drop.But it will start when it reach 69 degree. What is the problem?


Debra October 15, 2014 at 2:57 pm

Honeywell thermostat digital bout 3 years old installed by professional heating and air contractor burned up and shorted out last night. Is this normal can you replace thermostat with no worries or do you nee! Place service call and get it inspected. It did set off smoke detector


michelle wall September 30, 2014 at 6:41 pm

hi i live in a mobile home with a older outside ac/heat unit and the older thermostat we had problems in the summer with the ac pump freezing up and it was the drain well today the weather got warm in the 80s again (i live in NC) and it worked fine then froze again so we cleaned the drain worked great but the ac wouldnt kick off even after it was cool in my house so i cut it off myself well it got warm inside again maybe 2 hours later and we turned the ac back on and its back to freezing up again any ideas?


Justin Whipple September 29, 2014 at 3:22 am

My electric thermostat is set to 78, but the unit doesn’t shut off right away when it reaches that temperature. Any suggestions?


Cait July 22, 2014 at 10:03 am


I live in FL and during the summer it gets up to about 100 degrees outside, so throughout June july and august we have it running at around 78 degrees. We had a storm a couple of weeks ago where power got knocked off for about an hour or two. When it came back on we found out the AC wasnt working right. The outside fan is running and I can feel cold air coming from the vents but it is still REALLY hot inside (our thermostat reads as high as 83 in the house at 7pm). I am wondering if maybe the thermostat got friend and needs replacing or it sounds like a more serious issue? Really don’t have money right now to call out an HVAC tech so I think i might try and replace the thermostat first. Any ideas?


Jon Casey July 16, 2014 at 8:46 pm

The room temperature was reading at 80 when I turned on the A/C and set it to 70. The room got really cold, but the room temperature did not drop from 80. The A/C continued to run until I had to turn it off. I used it for a few more days and the room temperature continued to stay at 80. The A/C was running non-stop because the room temperature will not drop from 80.

Then I decided to reset the thermostat with the pinhole. Now the room temperature reads as zero and the A/C will not turn on at all. I tried the heat and that doesn’t turn on either.

I don’t know if this matters, but I live in a newly built apartment building and I think the HVAC unit is the heat pump type. Also, since the A/C was actually still working before I reset the thermostat, I’m guessing nothing is wrong with the HVAC unit itself. The thermostat doesn’t show any error codes and seems to be functioning normally except for the room temperature reading… It is an electronic programmable thermostat. The brand is Controlled Air Systems. The model is T21-B3B11.



Gena Dixon August 20, 2014 at 11:41 pm

When you reset it you unprogrammed it


Alayyan July 6, 2014 at 8:40 pm

I have Trane thermostat which doesn’t read the temperature write ( the room very cold but the thermostat showing high temp) , the technician informed me that I need to replace the control board along with the thermostat , is this replacing the control board is right thing ? I feel that I can replace the thermostat only


Jeff Gordon July 4, 2014 at 7:11 pm

Cooling unit runs and cools on auto, but on cool the fan turns but it doesn’t force cool air through the vents. Thermostat?


Kristina June 21, 2014 at 8:32 am

We recently just replaced our thermostat because when we turned our air on it would stay on and would not shut off when the set temperature was reached. Our bill was outrageous.

After we hooked up the new one, we now notice that the house wont get cool. we had no problem with this before. we were actually shocked at how cold the air was.

So how do i make my house cool again? maybe the coil is failing because of a tripped circuit? Could someone please email me?

Thank you very much!


Janelle seghers June 12, 2014 at 9:50 am

My honeywell thermostat was blinking low battery, when I went to change the batteries I couldn’t find where to just remove the batteries so I took off the thermostat completely from wall. I replaced the batteries and put thermostat back on wall and now it won’t turn back on I have no idea what to do.please help


cynthia June 6, 2014 at 5:32 am

So we just replaced the blower control board on both our upstairs and downstairs units we were told they were hit by lightening, now both systems are working somewhat….I can’t adjust the thermostat over 79 or it gets hotter if set at 79 then it stays okay could this be the thermostat?


Betsey May 16, 2014 at 5:23 pm

This is probably was off base with the thermostat but I just need some answers or opinions, please! I will set my thermostat downstairs on 70 and it will NOT go below 73. It was working fine until last night I bought a new filter, just like the previous one, and that’s when it started. Any ideas??


Reb June 24, 2014 at 1:13 pm

It probably cannot cool it in the summer heat below 73. People need to understand AC units just cannot cool that low when it is hot outside. If you want your AC to freeze up, keep running it low like that and you will have to pay to replace it.


Marco May 13, 2014 at 8:55 pm

I’ve set the temperature and everything but the ac does not turn on .


Roe Perrone May 13, 2014 at 5:14 am

I installed a new Honeywell Thermostat in January and it worked all winter on “Auto” yesterday when I turned on the AC it does not work on “Auto” I have to keep it “On” so it always running. Please Help.


Tracy June 11, 2014 at 7:10 pm

I have this same issue!


Lee May 8, 2014 at 6:36 pm

I have a Honeywell RTH230B Programmable T-stat. Since last summer (when using the A/C), the A/C won’t shut off. I have it set at 70 degrees and it never comes close to getting that cool. Today it’s 80 outside, the t-stat is reading 78 and I have it on 70. I can’t afford to keep it running, so I manually shut the t-stat off until I can’t stand it anymore, then turn it back on. I had a service tech out today, thinking the issue was that we needed more Freon. He said everything at the central air unit is perfect. He found that we had a dirty filter in the furnace (we always do, ever since we moved it, I don’t know why). He changed that for us.

So, if it’s not the A/C, is it the thermostat?


Jessica K April 18, 2014 at 8:20 pm

I bought a Honeywell digital thermostat before winter to assist with temp control and it worked like a champ with the furnace. Recently we had a hot day and I switched it over to cool and nothing. The a/c didn’t come on at all. This makes no sense to me. The a/c itself is fine; it was just checked out right before winter. I am frustrated because we have a warm week ahead and my mobile home becomes a sauna. My father also just went through heart failure and needs to stays cool. I need help ASAP!!


d May 28, 2014 at 1:46 pm

having the same problem and cant figure it out hope u come up with a solution if i do i will let u know


Y. Carter March 3, 2014 at 11:47 am

I have been living in my condo for almost 4 years. I have a honeywell thermostat which was new with the apartment. My utility bill is always very high even when I turn off the thermostat when I am not home (and I am not home sometimes for days). When I called the utility company, they informed me that the thermostat was “not all the way off”. I had no idea what that meant. I also noticed that the thermostat is usually several degrees higher than what the room temperature actually is. HELP!!!!!


Devon Daniel February 15, 2014 at 10:21 am

I have a 3 year old programmable Honeywell thermostat. When I set the thermostat to heat or cool while the fan is set to auto, I here the small beep from the thermostat, but nothing happens with the AC. If I switch the fan to on, it starts blowing but no cool or hot air (it’s seems like).

Also on the screen it doesn’t show heat or cool like it normally would. Is this a thermostat issue or relay? I want to say thermostat and I hope it’s that simple.


Victoria Miller February 6, 2014 at 6:12 pm

Hello. We have several thermostats failing. All were put in at same time and professionally installed. All suddenly have black streaks going from top vents up wall and two all the way to the ceiling….the higher temp rooms. Our heat settings are usually 60-64. I took one off and opened the inside and the circuit board is slightly blackened on each side of the small rectangular pieces attached to the board right near the vents. All ceiling heat has been shut off. And of course it snowed. Love light bulbs and gas fireplace. My question: can thermostat failure, as mentioned cause a fire? The circuit breakers did not flip off and I know the streaks are very recent. Thank you for your help. I read through all entries until the last one that finally mentioned our problem, but you did not discuss fire risks with this issue. Hope this helps some other readers. Victoria


Angelo January 27, 2014 at 11:04 am

I have a Honeywell programmable thermostat. It clicks when temperature is reached to kick on the furnace but the furnace does not kick on. I noticed one of my green flashing lights in the furnace inspection window was flashing so I went to the electrical box and flipped the circuit breaker off and then on and the furnace kicks on. Is this a thermostat problem or furnace problem?


ma lee July 18, 2014 at 7:44 am

did you figure out the problem, i have the same problem and it keeps occurring on and off


Denise January 21, 2014 at 6:51 pm

My thermostat reads a temp on the left hand side but is blank on the right(desired temp) This has resulted in furnace not turning on. Help, it’s minus 20 celcius.


gural January 15, 2014 at 12:08 pm

my thermostst works for cold ,but when i rise temp it does not blow hot air, no heat, i see two mercury tubes in it, if i raise temp all the way they tilt to other side but still no heat , is it the thermostst or furnace not working.


Crystal January 9, 2014 at 9:27 am

Our thermostat is set to 68 but it is 87 in our home. The heat never shuts off unless I turn the switch off on the furnace. When I turn heat off on thermostat the heat continues to blow out. Is this the thermostat or the furnace?


Brandon January 9, 2014 at 10:53 pm

I have the same problem. I had a new furnace installed yesterday morning and the temperature in the house is about 10 above the electric T-stat setting yet the fan is still running on the furnace. Let me know if you figure out a fix!


ben January 10, 2014 at 3:45 pm

That has got to be costing you a lot of a cash. Check the thermostat immediately that may be the only problem but could be more. Sounds like components in the thermostat are fried; cannot be repaired must be replaced.


Joe May 25, 2014 at 4:10 am

The Hot/Cold (swicth) or component is burn and the thermostat is total off, no ligths can be seesn or ligths. I had a therm… that was remove for a new and thathone replace the burn and nothing happen. Outside is ok!. What may be the problem here!. Thank you


Amber January 21, 2014 at 6:20 am

Crystal, last winter our heat went out one day, so i called my landlord and she sent a heating/air repair man. He fixed the problem and left my hpuse with the heat working wonderfully. A few hours later during early-mid afternoon i realized it was getting hot in my house despite the outside temp of 30°. My heat wouldnt turn off. So i called the man back and told him the problem and he said he’d come back out. He showed up about 2 hours later, and by that time i had all of my windows open because it was so hot inside my house. My heat wouldnt turn off at all. He ended up replacing some tiny little part in/by the furnace that apparently regulates the heat and gives it the ability to turn on and off. It took him all of 5 minutes and like i said it was just a tiny little part. Hope you get yours working properly!


Sarah Mystal January 7, 2014 at 10:15 pm

So last night I turned on the heat and after a couple of minutes it turned off the battery thingy kept flashing, I’m guessing it was telling me to change the batteries. So I put the thermostat off and changed the batteries but when I put the thermostat back on the wall at first it said “heat 2 pump” but it did not turn on it also made two clicking sounds. So I took the thermostat off the wall, took out the batteries for a couple of seconds then put them back in the thermostat and placed it back on the wall. Tried turning it on again this time it said heat pump and everything seemed normal but there was no clicking sound and it did not turn off. Is this a big problem? Do I have to call a professional to cone check it out? And also is this affecting my electricity bill in any way? Please help. Thank you


Rj January 14, 2014 at 8:14 pm

Its definitely affecting your bill if it won’t turn off automatically. Have a license professional come out and service your thermostat. Sometimes when you change your batteries you can throw off the levelness of the thermostat also turning it up and down manually is not good with some units because its a certain time before it will reset itself before actually coming back on. I recommend a license professional to come service you thermostat.


Tom January 7, 2014 at 12:50 pm

Hello Karie:

I have a dual unit furnace/Ac system. The bottom unit which is older is working fine. The newer upstairs unit does not bring the room temperature to the temperature set at the thermostat. I have turned the thermostat off as well as the unit at the breaker box, waited 15 minutes, turned everything back on and there is still 5-7 degrees difference, i.e. set at 68, temp. 61. Again, only on the upper floor, not on the first floor or basement. The thermostat is a Honeywell, same for both units. Any and all suggestions greatly appreciated.


Rj January 14, 2014 at 8:22 pm

We have the same unit. Do you have 2 thermostats 1 controlling the upstairs & 1 controlling downstairs?


Anita carter January 4, 2014 at 10:24 pm

My house has been freezing I replaced my thermostat because the old one would be set at 80 degrees and the house temp would only go to 69 degrees. I got a new Honeywell programmable thermostat install and I still having the same problem I set it for 78 and the temp is 69 the heat will not come on until I switch it off and then back on…. Please help should i have the central unit look at.


LATONDA KIMBREW January 21, 2014 at 1:15 pm

Hello Anita,
Im having the same issue and yes i brought a programmable honeywell thermostat. It ran great for the first day and then it was back to the same have to turn it off to have the furnace click on. Do you find an answer to your issue yet?


autumn November 12, 2014 at 8:32 am

hello, this is my first winter in this house and i have my thermostat set to 90 degrees however it wont raise above 76 degrees, my change battery button is on , would that have anything to do with it. plkz help its cold and i have three little ones.


Chris January 23, 2014 at 3:40 am

My tenant sets thermostat at 90 to get the room temperature to 65. It is a programmable Luz thermostat. The plumber says the water is circulating properly through radiators but not producing the heat. Please advise.


Susan January 4, 2014 at 7:09 pm

I have a Honeywell TH50018270002 digital thermometer. The inside temp reads 60 and it is set at 70! If I set the temp at 75 the inside temp goes up to 64!

Thanks for your help


Dayana January 3, 2014 at 8:13 pm

Hello I just rented an apt in nyc and it has its own thermostat I set it to 90 and the apt feels like 60, what’s going on? Help


sergio January 1, 2014 at 7:08 pm

I have a honeywell thermostat the round one and I have an older burnham boiler the thermostat is set at 70 but the temp reading never goes over 61 please help I just bought the house and this is my first winter in the home.


Karie Fay January 5, 2014 at 12:41 am

Hi Sergio,

Have you taken the room temperature with an independent thermostat and compared the actual room temperature to the thermostat?

I would also suggest reading the section above on the room temperature not matching the thermostat.

I would recommend trying to adjust the thermostat first. Do you have an owner’s manual? I am uncertain what kind you have, so if you have any questions about the thermostat itself, try looking up the owner’s instructions.

If all else fails, why not get a new thermostat? It may be just the opportunity for you to get a really nice one. Installation is usually fairly simple as well. It should fix the problem.

Congratulations on your new house –
Karie Fay


Linda December 26, 2013 at 1:13 pm

Today our furnace started by it’s self the temp was set at 56 and the room temp was 62. Sometime through the day the heat came on by it’s self with out us changing the temp. When we found this we tried to turn it off and it would not turn off. The only way that we could get the system shut down was the breaker. What should we be looking for as the problem??? It is a Honeywell Programmable.


Jessica December 31, 2013 at 1:21 pm

My unit is doing the same thing. We encountered this problem a little over a week ago and replaced our thermostat because the other was so old. Today the same problem has started. It is set on 72 and i realized it was still running at 76 degrees. Have you figured out what the problem is with yours and how did you repair it? Any suggestion would be appreciated as we rent our home and our landlord is on vacation


Karie Fay January 5, 2014 at 1:04 am

Hi Linda and Jessica,

I am suspecting you have problems with your thermostats, but it’s always possible that a furnace that won’t shut off without turning off the breaker could have a problem with the furnace itself.

Here’s what I recommend. First, look at your thermostat manual and make sure the temperature is set correctly. Remember you have “deadband” as explained above.

To see if you have a bad thermostat, you can have someone with some experience and a multimeter perform the following test as Don Vandervort of HomeTips suggests:

Turn the power off to the furnace and remove the thermostat or thermostat cover to reveal the wires.

Unscrew then remove the two wires connected to their terminals. Don’t lose the wires! If there’s more than two wires, choose the red and the white, which are standard for power and heat.

Wrap the two wires together then turn the power back on at the breaker and watch the furnace. As HomeTips explains, “If the blower goes on and the furnace burner ignites, the thermostat is defective. Replace it.”

If, however, the burner doesn’t ignite, also check the continuity of the wires running between the thermostat and furnace.

I am suspecting you both have bad thermostats.

Hope that helps,
Karie Fay


yvette December 8, 2013 at 9:54 am

I have a digital thermostat and its reading comm error. My unit comes on goes off until I raise the temperature.


Karie Fay December 13, 2013 at 8:56 pm

Hi Yvette,

It would help tremendously if I knew the thermostat manufacturer. Each one has their own codes and specific meanings. That said, I am guessing that you have a Communication Error, and that your thermostat is part of an HVAC system that is supposed to “talk” to each other. Do you have more than one thermostat in your home? So that you have different “zones?” This is one instance.

Since I don’t know the exact thermostat I can’t really tell you what to do. I would suggest you look up the manufacturer’s website and look for trouble or fault codes. If all else fails, email or call them.

Hope this helps,
Karie Fay


armin December 6, 2013 at 7:25 am

Every time I set my thermostat on any degrees (ie :73) as soon as it hits 73 , it set it to 70 by itself . wondering if you can help me to fix it


Sandy December 5, 2013 at 2:19 pm

My heat will not kick on unless I turn my thermostat to Fan for about 10 minutes then back to Auto and it will stay blowing until it reaches the thermostat temp….help???


mike December 2, 2013 at 7:43 pm

I have a programmable thermostat in my home and it keeps clicking sometimes for a min then I wont hear it for hrs but then it keeps clicking again the propane furnace is about 10 yrs old and seems to work just fine any ideas


Carl November 27, 2013 at 9:05 am

Can you help? when I set the thermostat temperature for heat on any number such as 73. When the temperature reach that level, the heating unit continue to run and will not turn off until I change the setting to 71 for example. Do you understand my problem? please advise.


sam November 25, 2013 at 2:42 pm

My furnace will come on then turn off. It will not come back on eventhought the mercury has fallen and should trigger the furnace to turn on. What’s up?



Jessica Fowler November 25, 2013 at 10:21 am

We have two thermostats controlling our boiler. The boiler seems to be working properly. The downstairs thermostat is working and the heat turns on as required to maintain the temperature. The upstairs thermostat is on and appears to be working, but the heat is not turning on and it is 63 degrees upstairs (set at 68). The thermostat displays the temp, and indicates “heat on” but the heat is not on. We replaced the batteries last night but this did not help at all. Any other suggestions before we call in a repair person?


Karla November 24, 2013 at 12:12 am

I just wanted to comment. We had built our house and a Hanna heating/ac system was installed. Worked great for about two years. Then the air conditioner kept turning off and on constantly and would blow warmer air at times. Had to pay $90 to find out that whoever installed it left some thick plastic wrapping inside I guess the machine! I was so mad! Hope this helps others.


Leo November 11, 2013 at 2:08 am

Hi Karie, Simple question, the room temperature indicated on my thermostat takes a long time to drop one degree, 3-4 hours at all times of the day or night. The dining, living room and din are insulated but the kitchen is not and has a door to close it off from the other rooms. But when I leave that door open to allow more heat to enter the kitchen, the thermostat does cycle more often, perhaps every 2-3 hours which is fine. But there are times when I wish the heat would kick on more often. I have it set at 63 during the night and 65 at a couple of wake up times in the morning, it just seems like it takes forever for the T’stat to drop 1 or 2 degrees. And the temperature does feel right at what its set at. After it runs 3-4 minutes and shuts off, the temp on the T’stat will continue to rise to 66 with a setting of 63. When it’s set at 65, the T’stat will rise to 68. It seems like its working ok but is it? I do understand raising the T’stat temperature will increase the cycles but I don’t want a huge bill. Any advice will be appreciated. Thank you for your time and have a pleasant winter.


Papillon Hanna November 12, 2013 at 11:01 pm

What you are seeing with your T’stat is called “Temperature Differential” If your T’stat is Digital, there is a setting for this.
The “Temperature Differential” setting adjusts your Unit to ‘kick-on’ or turn off within a preset range (1-3 degrees). For instance, If you set the temp at 65 degrees and the Differential is set for 3 degrees, your temperature will rise to 68* or fall to 62* before turning back on…. or before shutting down (if its running). Basically, it is keeping your temperature ‘around’ that 65 degrees you set it at (within that 3 degrees Differential)
You can adjust the Temp Differential to 1 degree, but that means your unit will run a lot more often. (If you set a 65* temp, when the T’stat drops to 64* it will ‘Kick on’.) My suggestion is a 2 or 3 degree “Temp. Diff.” to save on $ and over usage of the Unit.
Most importantly make sure your T’stat is NOT in a drafty area.
Hope you found this helpful.


Kate November 7, 2013 at 4:38 am

I’m Renting in the northeast right now and I’m having a problem with the anticipator thermostat. I have it off or at 50degrees but heat keeps coming out of the radiators, heat builds throught the day up to almost 80 and never gets below 75. I’m paying for it to be way to hot inside and have to open windows to let the heat escape at night. What should I do?


Kate November 7, 2013 at 4:39 am

Let me add that it clicks on and off fine… If I go up to the high temperatures.


Karie Fay December 13, 2013 at 7:15 pm

Hi Kate,

Are you still having problems with your radiators and the proper setting? Right now it may be cold enough that you’re glad for the extra heat of course. Still, if the problem continues, I suggest simply replacing your thermostat first. It’s a simple, cheap fix and I am guessing it could very well be the issue.

Good Luck!
Karie Fay


Brenda November 6, 2013 at 11:48 am

My mom has an old round thermostat. Put furnace on other day and it came on but did not heat house. I noticed the needle that tells you the temp of the house was all the way over to the left – it was not registering a temp at all. Even if we put the dial at a higher temp the furnace will not stay on. I believe it is the thermostat and if the needle is not even registering a temp, the furnace would have no need to stay on. However, my neighbor feels it is either the igniter or thermocouple on the furnace. Any ideas before I call a repairman for the furnace and incur a costly bill that a 20/25 new thermostat would possibly solve. Thank you


Karie Fay December 13, 2013 at 7:28 pm

Hi Brenda,

I think you knew the answer already. Before calling a repairman it is always best to try the simple things first. The *ancient* thermostat wasn’t reading a temperature at all. Replace it and the furnace will likely work as it should. Did you go ahead and do this? Would love to know more about how it turned out for you. Sorry I didn’t get to your question sooner.

Karie Fay


Paul November 4, 2013 at 10:55 am

My inducer fan works when the thermostat is set to ON and when I set it to AUTO it won’t start back up again the heater comes on a again.


Karie Fay December 13, 2013 at 7:18 pm

Hi Paul,

I am not quite sure I understand your problem. It would be great if you could give me further details.

Am I correct that your fan is not coming on and off when it is supposed to? So you are saying your furnace kicks on but nothing blows? If this is the case, I wonder if the problem is in the fan setting or the fan itself. Try looking at my article on troubleshooting a gas furnace. It’s listed under my articles – simply click my name in the list on the right side of this page.

Hope this helps,
Karie Fay


RICK HILL October 22, 2013 at 6:47 pm



Karie Fay October 30, 2013 at 10:35 pm

Hi Rick,

You mention you have a heat pump. Knowing that, you must have a special thermostat. I wonder if there’s a setback setting — a feature that drops the temperature at certain times of the night in order to save energy. Do you have the thermostat’s owners manual? Have you used this thermostat before, or is it a new thermostat (new house)?

My thinking is you might need a new thermostat. Especially given the age, it could be a simple fix. However, you should also check to see if there are settings affecting what you are experiencing first. Then try replacing the thermostat and see if that helps. Without more specific information, these are my best suggestions.

Karie Fay


Jane Pool October 19, 2013 at 6:14 am

I have a Honeywell programable thermostat. Yesterday I turned on the heat which I haven’t needed since last year. The unit kept running so turned everything off and it still kept running. Put settings to off and auto -still ran. Turned unit off then back on at the unit and turned the breaker off and back on -still kept running!Now I have the breaker off to keep the unit from running. Could the thermostat have gone bad ? It worked fine for air just did this when I switched to heat setting.


Karie Fay October 30, 2013 at 10:44 pm


I suspect it could be the same thing. Usually there’s two main causes for a furnace blower that won’t turn off unless you flip the breaker — a bad thermostat, and a faulty fan and limit controller. The fan and limit controller is an electronic component that controls the blower. Sometimes there’s a manual switch for it — it looks something like a light switch located near the furnace. If this switch is ON the blower will run constantly. Likewise, if the controller or the wiring leading to it is damaged, the blower will not turn off.

I would suggest looking for this switch first, then turn to the thermostat. I think you will find either way the solution is simple. Honeywell, for instance, has information about the controller online.

Hope this helps!
Karie Fay


joy October 11, 2013 at 4:20 pm

I replaced my upstairs thermostat yesterday and today when I went to turn on the A/C downstairs, it won’t go on. The fan set ‘on’ and ‘auto’work and the heat work. Any ideas?


Jessica October 9, 2013 at 9:18 pm

If my thermostat says 69 and I turn on the heat to let’s say 72. The room temp number counts down instead of up. So the heat can never cut itself off. Please help a guy installed this yesterday


Jerrylee October 6, 2013 at 10:01 pm

I hope you can help me figure something out. I have a Modular home with central HEAT. A new thermostat was installed a year ago (white Rodgers 1f80-362) I was not present during installation and no manual was left. I have the temp. set at 72.. during the day I turn the system off. 5 hours later, I am burning up in the house and current temp reads 76??. Do I need turn fan to on instead of auto?.. does the fan have anything to do with it at all??? help… its toooo hot in here!


Matt_in_Texas September 19, 2013 at 7:31 am

My RiteTemp programmable thermostat is not allowing me to adjust the temperature down and “clicks” when in the auto position. In fact, the temperature setting display blinks on and off randomly. I’m thinking there is a wire loose or the thermostat is not clearly communicating with the AC. I turned it to “on” and the AC came on as usual but is blowing the warmer air (the thermostat defaulted to 80 degrees). Is it the thermostat or the AC itself? Thanks.


joyce September 10, 2013 at 6:06 pm

same will not shut off even when it gets to tech out today.changed thermostat,thermal expansion valve and filter results.still running and i am sweating and electric meter is having drunken party zipping around and using up huge amounts of k w’ tells me it is possible something has damaged my ducts.hmmmm wonder what that will cost on top of my electric bill?


Tuan August 28, 2013 at 4:26 pm

Hi, I have a honeywell system. Temp is at 88, set to 75 but it keep staying at 88. I check the vent as air/fan is on but no cold air is blowing. Any suggestions? Thx.


Vicki August 20, 2013 at 8:35 pm

Thermostat set to 78 but is reading 90 and AC going off and on every 5 minutes.


Arpan August 19, 2013 at 12:50 pm

Question: The thermostat in the house indicates 76 degrees and it is set to 75 degrees. The AC is on but blower stopped blowing air. I tried next day with temps set to 70 degrees, and it worked fine. The problem surfaced again when the temperature in the house was about 1 degree higher than set temperature. The house would not get cold and AC continue to run with any air blowing. Is my thermostat going bad or the problem is bigger than that? Thanks for your help.


sandy August 19, 2013 at 8:38 am

Hello. Woke up this morning and my thermostat is reading “FL”……Does this mean that the filter needs to be replaced….Have been there 8 years and have never seen this.


Karie Fay December 13, 2013 at 7:26 pm

Hi Sandy,

I apologize for not getting to your question sooner. I do wish you had given me more information, such as the manufacturer of your thermostat, so I could give you more solid information in case you still need it.

Codes can vary so much from maker to maker. However, you should be able to search the manufacturer’s website for the information you need. Alternatively, try calling or emailing them with your query.

Hope that helps,
Karie Fay


david garcia August 17, 2013 at 7:47 am

My thermastat seems to be working fine. But i cant get my ac to shut down


dyan August 4, 2013 at 3:57 pm

ok My therm is set on 72 and feels really good in here. but will never go off cause the therm says it is 81 in here. I put a thermometer that goes outside to check it with and it say it is 74 in here. Help my bill is running into $400


David July 31, 2013 at 12:09 am

My Thermostat reads “hi” and will not turn on. Is this a problem with the thermostat or the air conditioner.


Hailey July 30, 2013 at 9:10 pm

Hi. Have a question my air has been running fine all day but when i went to bed I walked by my thermostat and noticed it had a blank screen like it was off but it wasn’t it was set to on so I went out side cked my air unit which wasn’t running next I cked the main breaker turned on and off still nothing. Do u think its just my thermostat? We have lived here for 3 years it was here when we moved here and the house is about 13 yrs old.


Kevin September 10, 2013 at 10:05 am

Have you replaced the batteries in the thermostat? If they go completely dead then nothing will work since the thermostat is the brain of the AC system.


Edgardo Abalos July 25, 2013 at 9:12 pm

My thermostat looks OK. It has all the digital display showing. I followed the instructions here. Cleaned/dusted the circuit board. Checked the fuse box, etc. The HVAC unit or my central air is not turning on even if I set the temperature to 75. Now the temp inside the house is 86. I wonder if there is something wrong with either the thermostat or the A/C unit. Please advise.


Stephanie July 22, 2013 at 11:56 am

I have a Hunter digital thermostat. Saturday morning I woke up to the thermostat flashing 90 degrees. No way the house was 90 degrees at the time. Some time later the flashing 90 was replaced with 83 degrees but a/c not working . Seems like compressor is not kicking in. Could this be a faulty thermostat?


Tom July 16, 2013 at 4:16 am


I live in the Northeast and I am noticing an issue with my thermostat. I have my AC set to 73 degrees. In the morning when I wake up it is 73 but as the day progresses it goes as high as 79 degrees in the house. My thermostat is set in my living room which has vaulted ceiling and the front of my home has the sun blasting on it all afternoon until about 8:30 in the evening. The strange part is that the house does not feel “hot” The temp on the thermostat will start to drop down after we go to bed and when I wake up in the morning it is back to 73. Is this normal in extreme heat situations? I also have a heat pump if that makes any difference. I could really use some help here if anyone has any ideas? Its driving me crazy. Thanks.


Karie Fay July 19, 2013 at 11:35 pm

Hi Tom!

In my opinion, it’s nothing to be alarmed about. Try setting a thermometer in your living room and monitor how much the temperature is fluctuating and if it matches the thermostat reading. It IS really hot this summer, and it sounds like your living room would take on a lot of heat. If you climbed a ladder to get up near the ceiling, you would find it’s easily several degrees warmer there. I live in Michigan, and my second floor is about 10 degrees warmer I would guess.

If you have any further questions, feel free to ask. I am curious about your temperature reading.

Hope that helps!
Karie Fay


April July 15, 2013 at 3:41 pm

We live in CA and it gets quite hot during the day, but cools down nicely at night. By 11am, the house will already be 82 degrees, so I kick the AC on for 79. It will take 3 1/2 hours to bring the temperature to 79. But it only stays off for 5-9 minutes before the thermostat reads the temperature went up to 80, and it will run for another hour to two hours before shutting off again. Is this normal? Just seems odd it only kicks off for a matter of minutes before turning on again.


John M July 11, 2013 at 8:00 pm

Hi there,

I just had a new thermostat put in at my apartment and my issue is that I will turn on the air when the temperature is 78. The programmed temperature is for 76. It will go from 78 to 77 in about 20 minutes but then run for 1- 1 1/2 hours and never reach 76 so it never shuts off. I can’t continue this or my bill will be huge. What would cause this and what is the fix? It is not on a hold temp or anything just normal running. Please help!


nick July 6, 2013 at 3:05 am

my thermostat only turns on if the temp is 10 degrees below the shown temp and turn off 10 degrees above shown temp


Melissa spencer June 28, 2013 at 3:56 am

my ac keeps trying to shut off. every hr or so it tries to kick off and the thermostat will spark and or and it just keeps trying till eventually it just turns back on and keeps runnning.. Do I need to replace the thermostat or how can I fix this?


Karie Fay July 5, 2013 at 3:48 am

Hi Melissa,

Unfortunately, that’s not a simple answer. What kind of thermostat do you have? If it’s a programmable t-stat, I would try resetting it first. Pop the cover off and look for a reset button and simply push it. You could also try changing the batteries if applicable. It’s a simple thing to eliminate.

The next thing I would try is making sure the t-stat isn’t filled with dust and dirt, so it gets good air flow. Maybe pull it from the wall and examine the wiring to see if you find a loose wire or any scorching such as would be caused by a short.

It’s also possible that it’s a bad contactor — a big relay that controls the flow of power to the unit and other electrical items on the circuit. If you can locate your contactor, you can try pulling the wire loose where it enters it. If the AC stops I would suspect the thermostat. If only turning off power at the breaker or fuse box makes the AC unit stop, I would suspect the contactor instead.

Sometimes the compressor can fail and cause similar problems too. However, I would look at the simplest possibilities first. I would also check the t-stat settings and blower settings. Check that it’s the unit running, not just the blower. While you likely already thought of these things, it doesn’t hurt to double check.

If you can’t locate the problem still, you could try hooking up a new thermostat. Alternatively, have someone check out your system. A volt/ohm meter is useful for testing power to the t-stat and someone knowledgeable can switch the wiring leading to the t-stat to eliminate each possible cause.

Hope this helps,
Karie Fay


Gare June 22, 2013 at 6:13 am

We replaced a non-programmable thermostat from 2003 in 2012 due to the buttons wearing out and not letting us change the temps, however, when it would work, we always got cold air in summer and warm air in winter. Now with the new programmable, we have noticed that even though we are setting room temp to 75 or 72 or whatever it will be, we will get the AC to reach that temp. However, the unit now also alternatively blows warm air into the unit which would seem counterintuitive in trying to keep the home a constant cooler temperature. We’ve had the AC specialists come out who installed the new theromstat and they say this is the thermostat’s energy-saving feature. I’m sorry, but I hate when I feel blasts of hot air coming in the unit when I want to keep the home at 72 or 75. The AC specialists have checked everything else and everything seems to be in working order. Madness, I say. Is this really how a new programmable thermostat should be working?


Karie Fay July 5, 2013 at 3:07 am

Hi Gare,

What kind of thermostat do you have? I am wondering if it has a sensor system that recognizes when you are in the room or leave it (in which case the room warms up). It may also have an energy-saving setting that’s kicking in? If you give me more details I can determine more. I would think the specialists should know, however. Did you ask them to explain it?

Karie Fay


Kai June 19, 2013 at 6:24 pm

I live in a 2 bedroom apartment and the thermostat registers higher than the temp. I mean just now (why I am looking up issues) I was freezing and I looked and it is set on 74 (due to roommate setting it lower again. Yes this is a constant argument) but it says 77 on the thermostat. I promise you, there is no way it is 77. I put my clock with the temperature feature on it in the bathroom and it said 69. I don’t know much about thermostats but I honestly think she is doing something to it. It is constantly a freezer in here but the thermostat says mid to higher 70′s and never goes lower, air is on all the time and our light bill has doubled. The thermostat says Trane and has a digital display. That is all I know about it.


Karie Fay June 30, 2013 at 9:32 pm

Hi Kai!

Sorry to hear you are having problems with your thermostat…. and your roommate. I tend to think the two aren’t connected, and the problems between you no doubt make you suspicious. However, I think your thermostat simply needs replacing. Do you have a landlord around? Try asking the landlord to take a look… If they are unwilling or unable to do so, you might think about grabbing a male friend or family member with some general DIY experience and have them install a new thermostat for you. (Make sure your landlord is ok with this… if the expense is on you, it may make them more agreeable to the repair.)

Hope this helps — and good luck!
Karie Fay


Amado Eligado June 14, 2013 at 9:21 pm

I have a Honeywell thermostat and its about 5 years old. when I turned the AC on and set the target temp, it shuts off before reaching the target temp. IE: room temp is 87 and target temp. is set for 78. It shuts down in less than 5 minuets and the room temp remains the same. I did check to see if it was blowing cool air and it was. Is it the thermostat or the AC. Thanks Amado


Gina Marion July 5, 2013 at 8:38 am

Did you change the thermostat? Did it help? I am having almost the same problem…..


Lucinda June 8, 2013 at 11:25 pm

My Totalline P374-1100 thermostat has recently started to cut off intermediately when it reaches the set temperature. It cuts off before the set temperature has time to adjust and circulate cooler air. This makes it uncomfortable and muggy. It does not feel cool. Is it time to replace this thermostat. Everything else has checked out fine. AC company does not know what is wrong. Everything reading properly.


Kat June 4, 2013 at 2:47 pm

I replaced our old 1960s thermostat last year and it all seemed to go great. Both the ac and the heat kicked on when I switched them on. Now it is getting warmer and my central air unit won’t kick on automatically. It will turn on if I turn the switch from off to cool and the temp is on the right setting, etc. but once it cools down the house and turn off that’s it. It won’t kick back on by itself. The furnace blower does however kick on when the temp goes higher. Just the AC unit outside won’t. If I turn it off and on again it will. Did I do something wrong with the wiring? Please help! Thanks!


Kenny June 3, 2013 at 8:41 am

New heat pump . Set thermostat to 75 . When house reaches 75 the compressor shuts off The house feels much cooler but the thermostat still shows 75. The compressor will turn on without going over 75 . It never shows below 75 ? Electric heat pump


carmen May 31, 2013 at 2:17 pm

I have a ritetemp thermostat and its about 5 years old. when I turned the AC on and set the target temp, it shuts off before reaching the target temp. IE: room temp is 83 and target temp. is set for 78. It shuts down in less than 5 minuets and the room temp remains the same. I did check to see if it was blowing cool air and it was. Is it the thermostat or the AC. Thanks Carmen


Ed May 31, 2013 at 6:49 am

Hi, I put a new circuit board in my furnace about a month ago. I had to use a universal board rather than the exact same one. the heat works fine. I am now turning the air on and it seems to me that the temp on the thermostat is going up instead of down like it should be. As the house cools the temp on the thermostat rises. I’m 99% sure that I have all the wires exactly where they should be on the circuit board. Could I have crossed wires? Or does this sound like a thermostat issue? Thank you.


Bailey July 4, 2013 at 3:14 am

Anybody answer this one ? I’m having the same similar issue


Karie Fay July 5, 2013 at 1:52 am


I would be willing to bet it’s nothing more than a bad thermostat. Specifically, a bad resistor in the current thermostat typically. As inexpensive as thermostats are, I would go ahead and buy a new one, wire it up, and see if that does indeed fix the problem.

Hope that helps,
Karie Fay


Ashley May 21, 2013 at 4:46 pm

We have a digital thermostat on our second floor. It doesn’t work all day (no display, no power) but kicks on around 8 pm and works through the night. We think it has something to do with the heat but we aren’t sure why.


linda May 15, 2013 at 3:07 pm

I have an old thermostat that control heat and a/c. The same unit control my 3 level home needless to say it is never the same temp on all 3 floors. Today I went to put a/c on and nothing unit “clcked”but no a/c I tried turning heat on just to test same issue, click but no heat. Never had this problem! Any suggestions?.


Karie Fay May 18, 2013 at 8:18 pm

Hi Linda,

Thanks for the question. First, let me tell you that I am not surprised that different levels of your home are different temperatures. I live in a two-story townhouse, and the upstairs is ALWAYS a few degrees warmer than the downstairs. That’s great in the winter – in fact, I sometimes crack my window to let some cool air into my bedroom at night. In the summer, it’s miserable. The best suggestion I have for that is to get creative. Can you put a fan at the bottom of the stairs, angled toward the far wall of the staircase? It will shoot air up the stairs, and if you put another one at the top, it will suck the air in turn.

As for your problem, it’s possible for the cause to be one of several things, and at a distance I am not sure how much I can help you narrow it down. I would be interested to know the type of thermostat and the type of furnace. Also, does the fan come on if you turn it to “Fan On” instead of “Auto”?

Probably the first thing I would do, if you haven’t already, is look for a furnace “reset” button – or turn it off at the breaker and leave it off awhile before turning it back on. With most electronics and home appliances, this seems to be a magic cure-all for many things.

That said, with neither unit (heat and AC) working, I think the likely problem is that your system has an electrical supply problem -possibly with the transformer.

Inside your furnace is a plum-sized transformer. It takes the incoming 120 volts electricity and converts a portion of it to 24 volts. This low-voltage power is used to communicate with your thermostat and central air unit. It also powers the circuit board and other low-voltage circuits inside your HVAC system.

If it is a thermostat problem, instead of a power supply problem, that’s easily checked. Simply turn off the power to the furnace, then take the cover off your thermostat. Unscrew the unit from the wall and look for four wires that connect to screw terminals inside the thermostat. Make a drawing showing where each wire connects to ensure you can put it back together later. Then, connect the R or Rh wire to the W wire to bridge the wires and bypass the thermostat.

Turn your power back on and see if the furnace starts. If it does, your thermostat is bad – quite possible since you mentioned it is old. If it doesn’t start, there could be a break in your wiring between the furnace and t-stat, or it could be the transformer. Unless you know someone with a multimeter who has some knowledge of HVAC systems, it’s probably best to get a pro to look at it. (If it is the transformer, the part itself is fairly inexpensive – probably around $20 – and you may consider simply having a pro troubleshoot it and you do the labor.)

Hope this helps, good luck!
Karie Fay


Renee May 9, 2013 at 10:43 am

Hi. I live in the south where we rarely use our heat but I noticed over the winter our thermostat doesn’t seem to be working right. It’s one of the rectangle ones with the mercury inside. This winter we would set the heat at 68 and it would not shut off until it was about 73-74. Then when we switched it to air a few months ago we really noticed an issue. We keep the air at 65 every night but it only cools to 70. During the day we have it set anywhere between 70-72 depending on who sets it. The air won’t kick in until its about 77. I truly don’t think that temp is even correct because we will be sweating just doing nothing. I think everything about it is off, the temp it’s reading and everything else. Any suggestions?


Karie Fay May 18, 2013 at 11:26 pm

Hi Renee!

What part of the south do you live in? I spent 20 years in Arkansas and totally understand the need for cool air! Hopefully we can get this resolved for you.

From what you describe, my instinct is that you can solve all your problems with a new thermostat. Obviously your units are working – you say it gets warmer in the winter than what you set it for, so that’s better than being cold. However, your AC is not kicking on until it’s much warmer than you want – that’s bad. In both scenarios it’s about a 5 degree difference that you describe. That’s making me think the temperature spread is wrong. I assume that the thermostat isn’t new, and nothing has been done to it to change anything? If so, I suspect it could just be old – am I correct?

I think you will find a new thermostat – especially a programmable thermostat with a setback feature that allows you to program different temperatures at different times – will be worth the investment.

Also, you can double check your room temp with a different thermometer. In the south, it’s not just the heat, it’s the humidity. You might be sweating at 77 due to the mugginess. Just a guess.

Hope this information helps!
Karie Fay


gail price April 21, 2013 at 4:44 pm

I have a new heat pump ( one week old).I set the air on 74. At night it drops to 69. Shouldn’t the air remain 74?


Karie Fay May 18, 2013 at 11:17 pm

Hi Gail,

Thanks for the question. I would really like to get more detail from you. Did you have an HVAC technician install your heat pump? If not, who installed it? What are the temperatures at night outdoors? How well is your home insulated? Are you not noticing a temperature difference in the daytime as well?

My first thought is that there is a “spread” of 3 to 5 degrees, typically, on a thermostat. It can be worse than that if something is wrong with your thermostat installation. I would suggest comparing your temperature spread from day to night. If your spread is too far off, then it needs calibration – simple enough.

Are you using a thermostat designed for heat pumps? If not, that could pose problems, as would a faulty thermostat. A thermostat that isn’t level, one that’s located in a drafty spot, or even one full of dust can cause problems with your heat pump. If, for instance, it’s in a spot close to a heat source such as an appliance, it will think it’s warmer than it is and call for excessive cool air.

I would expect the temperature to be close to your thermostat setting – yes. I really need more information to say much more, however. I would check your thermostat and call the installer if you still had questions. Until then, try turning your thermostat a little higher to compensate.

Hope that helps,
Karie Fay


Precious March 21, 2013 at 10:58 am

hello everytime I turn my thermostat to a temperature it never read that it is at that temperature. for instance if I set my thermostat for 75 degrees it will show that it is only 69 to 70 degrees in the house. the thermostat is located about 10 feet from the balcony door. I live in a town home and it is a up stairs and downstairs set up. it is much warmer upstairs and really really cold downstairs. what are my best options to solve this problem please and thank you.


Karie Fay March 26, 2013 at 2:48 pm

Hi Precious,

Wow, what a great question! You didn’t mention what kind of thermostat it is, but I take it from your comment that it is by the balcony door, it is upstairs in your townhouse. Am I correct? I also wonder if it is a new thermostat, or has it always operated this way.

Anyway, no home thermometer or thermostat is entirely precise. Still, the variance you report is a lot. I would suggest some simple troubleshooting first. Is the true room temperature always below the displayed thermostat temperature, or is it always lower than what you set it for? Often little details, if you watch for the symptoms, can narrow down the possibilities.

When was the last time you changed your batteries? Are the batteries the right kind? If the thermostat calls for lithium batteries, for instance, then other batteries may cause problems.

Check to see if it is the correct thermostat. If you know it is new, is it possible that you have the wrong one? Wall and floor furnaces use milivolt thermostats which operate with thousandths of volts, while forced air systems use whole volts instead. If so, the thermostat can’t track your temperature correctly. This is less likely to be the problem — but still worth mentioning.

On an old thermostat the anticipator may need adjustment or may be bad (see the article section addressing the temperature not matching the room temp.). Digital thermostats are different, and if you eliminate every other cause, I would simply replace the thermostat.

As mentioned in the article, drafts and thermostat placement also effects the thermostat. Is it located on an outside wall? If it is, consider having a plate installed behind it to protect (insulate) it so the outside temp. doesn’t affect it as badly. Make sure it is level and clean, and check your furnace filters too! A system that isn’t running well may affect the thermostat temperature greatly.

Given the fairly low cost of a new thermostat, it may be easier to simply replace it if you can’t figure out the problem. Having a handy guy put it in for you is less expensive than a service call!

As for the upstairs feeling so much warmer — welcome to my world. I live in a town house currently and the bedrooms upstairs are warm when they should be cool (summer) and warm in the winter too. And my thermostat is downstairs.

Don’t block off your vents to try to fix it. It seems the best solution, for me, is to set a fan at the bottom of the stairs and another at top to suck some air between the two. I suspect better insulation would help if you own your town house. However, given that heat rises, there will always be some difference.

Hope this helps,
Karie Fay


Kaylynne February 22, 2013 at 3:19 pm

I’m thinking my thermostat needs to be replaced. It’s digital and at least 4 years old. We’ll set it to a temperature, say 72 degrees, and if it is 75 in the house at the time, the air conditioner will turn on but will stay on until it’s around 68 degrees. If it’s cold and I turn it up, it will go up several degrees past the “target” temperature. It’s really frustrating because I’m sure we’re wasting tons of money with it constantly going in extremes. Every once in a while, it won’t kick on at all. Thoughts?


Karie Fay March 11, 2013 at 5:12 pm

Hi Kaylynne!

Thanks for the question. In electromagnetic thermostats, simply adjusting the heat anticipator will change the temperature spread — technically known as the temperature differential — that controls at what temperature your system kicks on, and when it kicks off again. A 7-degree spread, as you indicated, is way too much. (Incidentally, the human body can discern the difference in 1.5 degrees of temperature change.)

You didn’t mention the brand or model of your digital thermostat. However, it probably doesn’t have a heat anticipator, but a timer chip and temperature sensor instead.

On some digital thermostats you can electronically program your temperature spread. With others, you may need to change the cycles per hour instead. As you increase the cycles, you lessen the temperature spread. Decrease the cycles and you make the temperature spread larger.

Try calling the manufacturer and asking how to adjust your thermostat. You might be able to find instructions online as well. If the thermostat still doesn’t work properly, the chip or sensor might be bad. At that point, a new thermostat is probably your best option.

Hope this helps!
Karie Fay


Robert Villanueva February 7, 2013 at 7:17 pm

Question. What causes a black streak leading from the digital thermostat for a ceailing heat on the wall up to the ceiling. Black dust. And can it be a fire hazard?


Karie Fay February 16, 2013 at 2:35 am

Hi Robert,

I’ve been trying to figure out your problem. What you describe sounds highly unusual. Do you happen to know how old your thermostat is, and was it installed by a professional?

Ceiling heat was especially popular in the 1960s and 1970s when energy costs were much lower. It works much like an electric blanket — Electricity (220 volts) flows through your thermostat, up a wire, and into the wires spread across the ceiling. Older styles laid a web of wire that was then covered in plaster and sandwiched between two layers of drywall. New styles have variations, sometimes installing a wire mat instead, for instance, above the ceiling drywall instead.

A lot of homeowners have disconnected their ceiling heat because all it takes is one broken wire for the entire thing not to work. Finding the broken wire and splicing it is a real pain. However, there are few fires associated with the wiring, so I don’t think it’s likely that.

I would suspect either thermal tracking stains or a problem with your thermostat. Thermal tracking stains, in short, are areas where dust, soot, dirt — anything floating in your air — gathers on the walls due to that area of the wall being warmer. Since warmth contains higher moisture, contaminants in the air will cling to warm spots. Usually you see this as vertical stripes over large, insulated areas between cooler, stud-filled areas of the wall. Since you have a streak above a thermostat — by definition slightly warmer than the surrounding wall — it is possible this is the cause.

Frankly, I would keep that in mind but dig deeper. Take the cover off the thermostat and look inside for black “dust” particles inside. Turn off the breaker that supplies power to your thermostat and dismount it from the wall. Look at the wire where it connects to the thermostat and where it enters the wall. Thermostats do have a life expectancy and given the power that flows through it, I would make certain that the thermostat is okay. If you do decide to replace the thermostat (fairly inexpensive) ensure you purchase one compatible with ceiling heat — ie. a digital line voltage thermostat. I suggest having a professional look this over and replace the thermostat if necessary. 220volts is dangerous.

I don’t think the black dust is hazardous to your health or is it a fire hazard. I am concerned about your thermostat however.

Hope this helps!
Karie Fay


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