Central Air Conditioning and Heat Tips: Maintenance Made Easy

by on August 19, 2012Karie Fay

central air conditioning and heat tipsPicture a time before central heating or air conditioning, when fireplaces or crude stoves heated the center of the house or, if you were really lucky, perhaps the bedroom. Cooling in the summer was unheard of, unless you plunged into the river like Huckleberry Finn or could afford servants standing around fanning you like a member of royalty. Temperature was governed by the seasons, and humans simply learned to cope.

Today, in contrast, we have it easy. That is, it’s so easy that your heating and cooling system is often overlooked – almost an afterthought – until suddenly the furnace doesn’t heat or the cold air doesn’t blow. (And it’s kind of like a law that it has to break down when you need it most.) While there are no guarantees when you are dealing with mechanical equipment, understanding your system and scheduling proper preventative maintenance goes a long way toward keeping your heat and air system – often referred to as HVAC – healthy and strong.

How Your Air Conditioning and Heating Works

Furnaces and central air conditioning units are joined together and controlled first by the thermostat mounted somewhere inside your home. As the temperature rises or falls, the thermostat generates a signal to either the furnace or the central air via a small wire. The appliance, in response, turns on and prepares to deliver either hot or cold air.

A central air conditioning system circulates refrigerant through a condenser, located in the exterior portion of the central air unit, where it is first compressed and subsequently sent to the evaporator inside. There, the blower motor attached to the furnace forces air across the cold coils filled with compressed refrigerant. As the air blows, the coils heat up and the cool air is carried away. The now-warm refrigerant cycles back to the compressor again while the cold air flows out of the home’s vents.

Although there are many types of furnaces, each operates in a basic manner as well: When the thermostat signals the furnace that air temperatures have cooled, the furnace kicks on and turns up the heat source inside the appliance. Then, at a given temperature, a fan blows, forcing air across the now-heated elements. This heat subsequently escapes through the same ducts and vents the air conditioner uses in the summer. The furnace continues through a cycle before the heating stops, the air kicks off, and the unit waits again for the next signal.

Central Air Conditioning and Heat Efficiency

Up to half of your energy bill each month goes toward your heating and air conditioning, as the EPA explains. Today it’s more important than ever before, in light of rising energy costs and increasing environmental awareness, to operate an energy-efficient heating and cooling system.

Appliance efficiency relies on several factors: unit sizing, proper installation, ongoing maintenance, and basic energy-conserving practices inside the home. Most people have little influence on the installation, other than hiring a reputable professional qualified to perform the work (there’s really no short-cuts here; you get what you pay for). Regular inspection and maintenance, however, are elements directly in your control and require little time or money investment.

Energy experts suggest that the average homeowner can reduce heating and cooling costs by up to 30 percent with an efficient system. That’s a savings that your pocketbook will thank you for, as well as the Earth.

System Sizing

Don’t let anyone fool you – sizing either a furnace or a central air unit is complicated. While some homeowners and “backyard” installers try to take shortcuts, using a conversion chart or a simple calculation of a given number of BTUs per square foot of home area to determine the unit size, the results are often inaccurate, and inaccuracy translates into cost. As with professional installation, you get what you pay for, so spend the money to have the furnace and central air properly sized before buying a new unit or upgrading the one you have.

This is one of those cases where more and bigger is not better. Over-sized heating and air units reach the desired temperature too quickly, causing them to cycle on and off constantly, use more energy and, in the case of the air conditioner, fail to remove excess moisture. Undersized units struggle to keep up, often failing to maintain the desired temperature and running constantly in the process. Both conditions cause excessive wear and tear on the unit, higher electrical bills and more frequent service calls on top of a shortened life expectancy for the unit. Both your comfort and your wallet suffer.

A qualified HVAC technician will assess your house to determine the unit size you need, using your square footage and the average temperature in your area along with energy-loss factors such as the ceiling height, amount of shade, window area, amount of insulation in your home and more. A professional can also guide you in evaluating heating and cooling equipment, choosing the unit and efficiency level – called the SEER rating for air conditioning and the HSPF or AFUE rating for furnaces – best suited for your situation. While higher ratings indicate improved efficiency, these ratings reflect ideal, laboratory-created conditions. Real life situations usually vary far from ideal, meaning in some cases, the higher cost of the highest-rated unit may not be recouped in the energy savings achieved.

A word on choosing a heating and cooling professional: The cheapest, once again, may not be the one you want installing or working on your equipment. Before hiring any technician, ask around about the person or company’s reputation. Check with the Better Business Bureau to find any complaints. Find out what ongoing training the technician attends. Ask for a detailed estimate before the work is performed. Most importantly, ask how the work will be performed, step by step, and what tests and adjustments are necessary to assure safe and energy-efficient operations.

Central Air Conditioning and Heat Maintenance

A properly installed unit is only half the battle. Keep your system operating at peak efficiency and save on unnecessary repair bills by inspecting your system regularly. Ideally, hire a service professional to inspect your central air system at the beginning of summer and your central heat when it grows cold late in the year. While you can perform a system check yourself, HVAC contractors are better suited to take an in-depth look at your entire system. So-called “tune-ups” inspect and seal the duct work, if necessary, along with measuring the system’s air flow, measuring coolant levels and testing the compressor as well as other mechanical parts. At minimum, have an initial evaluation performed and repeat every few years as possible. In between, do your own inspections and maintenance.

  • Clean any exposed unit surfaces, both inside and out. Leaves, pine needles, vines and debris can quickly smother the central air unit outside and dust or hair can affect the furnace indoors.
  • Change filters at least twice a year or more often as needed. Glancing at your filters every month or two takes but a second and potentially saves you a tremendous amount of money.
  • Turn on the furnace or air conditioner in advance of the upcoming season and listen for abnormal sounds, smells or behavior. Consult a professional immediately if the system reacts alarmingly or emits strange sounds and odors.
  • Check your thermostat yearly to ensure accuracy. Simply compare the temperature reading to the display on another thermometer. Change batteries in programmable thermostats yearly as well to ensure consistent, proper heat and cooling control.

Troubleshooting Your Air Conditioning and Heat System

If your system refuses to work, try troubleshooting before calling a professional. Many times there’s a simple solution, and if the problem is more complex, at least you can point the technician in the right direction.

If your HVAC system doesn’t turn on, the first thing to check is the thermostat. Is it on and set properly? Is the blower control switch in the proper position? Has the temperature setting been accidentally moved? Try turning the thermostat on and off to reset the electronics and possibly fix the problem. In the worst case scenario when something needs replaced, the thermostat is what you want to fail. Installing a new one is a fairly easy repair.

Another common failure is a blown fuse or tripped breaker. Furnaces and central air units draw a tremendous amount of power. Older units draw even more, and older homes may have difficulty handling the demands. Look inside your home’s master electrical box to see if the fuse controlling the system is bad or if the breaker switch is out of alignment with the others. Replace or flip as necessary. Some units may have fuses and switches in other location near or inside the unit itself. Look beside the furnace for a blower switch or a furnace power control. Inspect the pilot light if the blower works but the air isn’t warm. Consult a professional for more information and in-depth repairs.

Sometimes a central air system simply freezes up. If the unit runs when the temperatures are too low outside, the system may be undersized or the coolant levels too low, among other causes. The unit can actually ice over and refuse to work immediately. The solution is turning off the air for a few hours and letting it warm up again. However, this may be a temporary fix at best as it is likely to freeze up again. Find a qualified professional to evaluate your system in the meantime.

Finally, understand that all things have a life expectancy – even your heating and cooling system. If major components fail or your system needs frequent repair, it may be time to send it to the appliance graveyard in the sky and purchase a newer, more efficient one. While many experts recommend replacing central heat and air units every 10 to 15 years, ones built before about 1980 are likely to be terribly inefficient. Balance the system cost against the potential repair and energy savings to make your final decision.

{ 47 comments… read them below or add one }

joey seeley February 10, 2015 at 3:31 pm

i have an old coil heated furnace and when the t stat calls for heat and the fan comes on and theres power to the fuses that run the coils but they dont come on. could it be one of the relays that the wiring goes to?


Eric February 3, 2015 at 6:36 pm

Our central heat hasn’t been turned on in 4 years. The AC has but the heat hasnt. Is it ok to turn it on?


Bob ligas December 23, 2014 at 7:32 am

Can anyone answer why my heat pump blower motor cycles properly during day with 40 degree weather outside with thermostat set at 70. At night though wife sets thermostat at 62 but the blower motor stays on all night with temperature at night at 20 ? Appreciate a answer.


Yan December 15, 2014 at 12:45 pm

My Heat works fine during the day, but at night, it blows out cool air, the temperature does NOT drop during the night, it stay whatever I set it to, but I just feel the air is not warm. However, during the day and in the moring, I can feel the warm air come out again, is there something wrong with that? or is that the way it suppose to be?


Bob ligas December 23, 2014 at 7:20 am

Mine does same thing, works on off during day but we turn it down at night 4 + degrees and blower stays on, especially in colder weather. Did you solve your problem? Send me a email if you can or reply somehow. bligas@bellsouth.net


Doreen weese December 6, 2014 at 12:52 pm

My central heat comes on for 90seconds every hour or so.the house feels very cool yet my thermostat reads 78 which the temp I need at my age


Kia K November 17, 2014 at 9:11 pm

During the summer or ac unit/central air worked great. Now that it is winter, we have switched over to heat. The thermostat is on heat and we’ve set it to about 68/70. The heat works fine but it is warmer upstairs than downstairs. The ac unit outside though seems to come on when the auto fan kicks in. Is this supposed to be happening? Is the ac unit outside supposed to be on or working?

Any advice would be awesome!


Lindsay November 1, 2014 at 12:08 pm

My central heat is blowing out cold air.


Sherry August 19, 2014 at 4:42 pm

The blower doesn’t shut off when my air conditioner shuts off. Anyone know why this would happen?


Donna June 29, 2014 at 7:28 am

We just upgraded to one of the new Lennox AC systems for our home. I wish we hadn’t. The new systems are like the “heat pumps” of the AC world. They cool the house but they don’t feel cool like the old ones do. I find I have to reduce the temperature by another 6 degrees to be comfortable. I’m not sure if it’s because of the newer coolants being used or because they reduce less humidity, but the comfort level is just not the same.


Denise July 17, 2014 at 10:39 am

Donna, We just installed 2 new Rheems units and are having the same issues. I’d love to talk to you via email about the issues you’ve had and how you’ve dealt with them!


cheryl June 19, 2014 at 9:14 pm

I turned my ac on for the first time the other day. I turned it off that night and the generator is continuing to blow air. The thermostat is set to auto for the fan and the ac is off. Why is it still blowing air a day later?


Sherry August 19, 2014 at 4:36 pm

I’m having the same problem. The blower is not shutting off when or just after the air conditioning unit shuts off. Anyone know why or have a solution?


Vivian June 18, 2014 at 7:24 am

A brand new AC unit w/ heat pump installed last year. Last 2 months the AC is running all day long in order to keep the house 73 degree but couldn’t make it during the day. Technician said everything is OK and he suggested to have the ceiling insulation(???). I am not convincing with his suggestion. A brand new unit couldn’t just turn bad in a year. Please give me some suggestions.


Chagrin June 13, 2014 at 4:26 pm

My , central air thermostat is on air. Switched to “ON” and set on 67 degrees which is my preferred temperature. Only hot air is coming out. The “FAN” is obviously what it is set on and it’s normally set between 64 and 70. The air conditioning of my central air unit is on and currently set to the average 67 degrees. The air blowing out of the vents feels quite cool and has been on nonstop for hours. However it is saying that it is 90 degrees in the house. I need help badly here.


Sophia May 25, 2014 at 3:03 pm

Can anyone help….The central air works perfectly fine in the house, when the inside cuts off when its cool enough…the outside fan still is running. I have replaced the fuse just in case…but I need to know what may be wrong and why the outside unit is not cutting off…

Please help


Jesus Romero May 14, 2014 at 10:50 pm

My hvac its one unit heat pump and ac every time I turn on the ac and I turn it off the compressor kicks and the blower motor stays on and the thermostat says off and in auto replace thermostat and contactor need help please


Christina brown May 11, 2014 at 11:32 am

I have central heat and air. But when I turn on the air (72 or 73) it runs for a bit. Then the unit goes off and immediately the heat comes on. Its a new unit about a year old. So why does that do it? If you could help please let me know. Thank you!

Christina Brown


Sara May 8, 2014 at 11:24 pm

I put a Baggie of plant food on my outside unit out of reach from my baby and forgot it and today it rained and it was making this really really loud annoying sound and started blowing out hot air with it set to cold! It sounded almost like someone was vacuuming all day! So I went outside and seen the plant food on it that I forgot and went to grab it and noticed it was HOT and some had leaked into the unit with the rain! So we tried spraying it off with a hose and it started smoking !! What do I do??


Jordan March 22, 2014 at 8:07 am

Will it hurt my HVAC unit to switch between heat and air in the same day? This morning it was very cold and I wanted to warm up the house, but now the temp outside is warming up and I need to switch to AC to keep the house comfortable. Is that bad for the system?


Pat February 3, 2014 at 11:35 am

This is my first winter in this house. When my central heat comes on it blows out cold air for about a minute and a half to two minutes. Then it warms up. I’ve never experienced this in the other houses I’ve lived in.


Sheri January 16, 2014 at 2:20 pm

My central (electric) unit will not work consistently. I turn it on, the inside unit comes on and eventually the outside unit will kick in and blow hot air. But, then you can hear something cut off and it’s still running outside but is only blowing cold air. A lilttle while later, if I’m lucky, something kicks on again outside and hot air is blowing again…help?


jen January 31, 2014 at 8:56 am

Your unit is in defrost mode. It kicks in when the coils freeze outside. It will sound sort of strange when its in defrost mode. During this the outside fan is “supposed” to stop until the defrost phase is complete. When it gets stuck what you are getting inside during defrost is lovely airconditioning in the middle of winter.

I had the same problem and they had to replace a board on my System. It was around $100. Then the next problem was the outside fan wouldn’t cut off period. I had to go out and pull the fuse. That ended up being a bad switch. The part was around $20.

Hope this helps


Sophia May 25, 2014 at 3:00 pm

@ Jen…

Do you know if that may be wrong here as well?…. The air works perfectly fine in the house, when the inside cuts off when its cool enough…the outside fan still is running and blowing out hot air…Please help


Derinda Gallimore January 1, 2014 at 7:17 pm

My heat pump heat strips are always heated up the fan comes on and the heat works and then it will shut off but when you walk by the inside unit you can smell the heat and it is hot why is it doing this ?


Karie Fay January 5, 2014 at 1:15 am

Hi Derinda,

I am curious how long you have had the heat pump and the thermostat? I am almost betting this a thermostat problem. You are right, the heat strips shouldn’t be on all the time, but only when that extra heat is needed. You can try removing the red wire from the thermostat and see if the strips go off (they should). If so, replace your thermostat.

Hope that helps,
Karie Fay


Ravan January 1, 2014 at 6:24 pm

My heat on my central unit works great until it gets really cold. Then, it won’t even come on. I tried turning it off for a few seconds and then turning it on, but that doesn’t work. I switched from auto to on but it just blows out cold air.


Karie Fay January 5, 2014 at 1:22 am

Hi Ravan,

How hot is the air coming out of your furnace vents when it isn’t cold? I am curious about that. In most cases there’s something wrong with the furnace itself if it blows cold air when it should blow hot — and that shouldn’t be affected by the temperature outdoors.

Could you give me more details about your furnace? Depending on whether it’s gas, electric or another type, the typical cause varies. i can say you will likely need a repair technician for this one.

Best of luck,
Karie Fay


Kaya November 4, 2013 at 1:42 am

I just moved into a new house which has central air for cooling but uses hot water baseboards for heat. I’ve never had central air before but every time I turn on the heat I feel the baseboard heaters turn on but can also feel cool air come out of the A\C vents. Am I going crazy?


Chandra October 21, 2013 at 10:19 am

I turned on my heat for the first time, but air is coming out. I tried to turn it up, but it jumps back to 61 degrees. I tried to shut it off completely, but it won’t go off and now it is freezing in the house. I even took the batteries out, but cold air is still runnung


Karie Fay October 30, 2013 at 10:19 pm

Hi Chandra,

I wish I had a few more details about your situation. What type of heater is it? What do you mean by it jumps back to 61 degrees? Is this the thermostat reading? Is it showing the temperature in the house as 61? And what won’t go off — the blower?

If it was just a matter of cold air blowing but the fan turned off when the cycle was over (going on my assumptions above) I would wonder if your pilot light was lit and the burner came on as appropriate. But if the fan is running continuously, I would wonder if it isn’t an issue with the thermostat. I would look at both of these before digging deeper. With more details, I may be able to help more as well.

Karie Fay


peter September 27, 2013 at 6:12 pm

My forced air heater has an issue. In the AUTO mode the heating element heats up then kicks off without tripping the fan on. Even in the Off position on the thermostat the heating element repeatedly heats up and shuts off with no fan. The fan works when you turn it to ventilate ON position on the thermostat. Do I need a new thermostat or is there a trip mechanism for the fan that needs replacing? Thanks.


Alan Rose March 12, 2014 at 8:57 pm

My unit just started doing this only it works when “ON” but the element continues to cycle when “OFF.” It is a Mortex.


tammy September 27, 2013 at 5:28 am

Do I have to remove the big fuse outside for my central air unit before I use my furnace? I have over the yrs before but I was recently told I didnt have to. Thanks for any help!


Karie Fay October 30, 2013 at 10:14 pm

Hi Tammy,

Interesting question. In all of my years I have never removed the central air unit’s fuse before running the furnace. In fact, in some southern climates there are days when you may choose to run the heat and air both, so removing a fuse would be pretty inconvenient. I would actually be more comfortable with you leaving that fuse in, only removing it for replacement.

Karie Fay


Brenda June 27, 2013 at 1:09 pm

My central air and also my when my heater is on hardly any air comes out of the vents. I have cleaned out everything including the round fan inside my heater. This was full of dirt and lint. Still my heater or central air produced hardly any air flow. What do you suggest that I do?


Brenda June 27, 2013 at 1:06 pm

My central air hardly blows out any air at all. I have cleaned all of the filters and even vacuumed out the main turn vent inside the heater. Still I can barely feel air coming out of my central air. I tried turning the heater on and I had the same results. No air. Is there anything I can do to fix it?


Bernard June 5, 2013 at 9:21 am

This is an interesting post I’ve seen on this subject. You really have a good feel on this topic, and the way you wrote about it made it both interesting to read, and informative at the same time. I’m glad I dropped by. I will definitely check back in the future to read more of your entries.


Bruce Whitehead June 2, 2013 at 11:02 am

My central A/C is only 3 yrs old but last yr & this yr it wouldn’t start up right away. Lines are iced up. How do you keep them from icing up. Lat yr the installer came back & fixed in no time but it happended again this yr.


danny May 22, 2013 at 4:54 pm

My inside blower is not working I changed the themosat now the inside blower is working but the air isn’t cold why


Sabrina March 30, 2013 at 11:51 am

My central air heater fan won’t shut off. I have taken the batteries out of the thermostat, shut off the thermostat, flipped the breaker, tapped the switch box.
The switch box has the winter/summer switch and a Master switch. when I shut off the Master switch it shuts off (as it should)…
I’m not sure what to do at this point. The thermostat seems to work as it heats up when I turn up the heat, and when I turn it down the air gets cooler.
I’m thinking its the fan switch.
Please help!


Karie Fay May 25, 2013 at 1:59 am

Hi Sabrina,

If I understand you correctly, your blower inside your furnace unit — which kicks on with heat or air conditioning, if you have it — won’t turn off as it should. Am I correct? It runs constantly instead of only when the heat kicks on?

I think you’re correct, it’s in the unit switch (the blower switch) rather than in the thermostat. I am assuming the unit has a switch with three positions – On, Auto and Off – and you have made sure it isn’t “On,” correct? That would also cause the problem. If it’s on Auto and all else fails, I would suggest having a professional look at it for you.

Hope that helps,


Herman Hill February 19, 2013 at 11:01 am

I need to know how can I get my heat to evenly to come down stairs.


Karie Fay March 11, 2013 at 10:19 pm

Hi Herman,

I am a little confused about your question. I would need more specifics to give you a precise answer.

In general, I can tell you that the upstairs will be warmer, year-round. I live in a two-story as well. In the summer it’s warmer, but in the winter it’s warmer too.

You can increase air flow between the two levels with a fan, pointed down the stairs or up, depending on the season. I also have a habit of blocking a vent or two either upstairs or down, again depending on the season. However, never block more than 20 percent of your heat or air vents. It will make your HVAC system more inefficient and isn’t good on the system. Vents are calculated to provide a precise amount of air flow, so you really need the ones you have.

I would also suggest upgrading your insulation, as necessary, and sealing air leaks as needed. That will help keep in what heat is downstairs.

Hope this gives you some ideas!
Karie Fay


Karie Fay February 7, 2013 at 1:30 am

Hi Pat,

That’s a difficult question. There are so many things that affect your heating performance that without looking at it – or at least knowing more about it – it’s impossible for me to say precisely.

For instance, even if your furnace is operating properly, if you don’t have enough insulation and if you haven’t air-sealed your home, in subfreezing temperatures it may indeed be hard for the furnace to keep up. If your furnace is undersized, it also will not be able to obtain the needed temperature.

In most cases, however, I would expect your home is reasonably weather-tight and your furnace adequate for the area. If so, you have to look closer at the thermostat and furnace. Have you found my articles on troubleshooting a gas furnace and troubleshooting a thermostat, on this blog? They are informative places to start.

If the anticipator is off inside your thermostat, then this will affect your temperatures. Adjust the anticipator and see if that fixes the problem.

A useful diagnostic test is to measure the temperature rise associated with your furnace. To do this, first find the temperature of the air in the heat register closest to your furnace. Don’t let the thermometer touch the duct sides during the test, and make sure your furnace stays running. Then, take the room temperatures.Subtract the room temperature from the hot air temperature to find the temperature rise. The result should compare to the temperature rise listed on the furnace’s data plate, located on the front of the furnace.

If you find an extreme variation between your results and the listed temperature rise, you could have a dirty filter or a problem with your burners or fuel delivery system. A professional can pinpoint the problem – but you can narrow down the possibilities as outlined first to save money.

Hope that helps and you manage to stay warm!
Karie Fay


pat January 25, 2013 at 3:35 pm

if the temp you set it on does not get to, say you set it at 72 and it won’t get higher then 66 what could be the reason—it been very cold could that be the reason(in the lo 20′s)


Melo Air March 10, 2013 at 8:44 am

If you are using a heat pump and electric strip heat, 66 degrees indoor temperature when it is in the 20′s outside is what to expect and the equipment is performing according to specs. Heat pumps are not designed to overcome a more than 40 degree temperature difference. 25 – 30 degreed above the outside temp is what to reasonably expect when heating with a heat pump.


Leave a Comment