Central Air Conditioner Not Working? Try These Simple Troubleshooting Steps
Our central air conditioner unit is over 15 years old and recently it hasn’t been working quite as reliably as we’d like. Even though I’ve been doing my best to care for my central air conditioner is appears that mine might on its way out. About once every couple of days now it simply “stops” coming on and I have to try a bunch of different things to get it working again. I was planning on getting a new central air conditioner in the next year or two anyway, but it looks like I may be doing it a little earlier than I had anticipated.
Without getting too technical I thought I’d share with you a couple steps you can try before calling in the air conditional repair (or sales) guys:
1. Make sure you’re setting the AC thermostat properly: Some thermostats don’t immediately turn on the unit and some have a 2 or 3 degree temperature “window” they use to gauge whether the air conditioner should switch on or not.
2. Make sure your AC thermostat is working well: A lot of homes have electronic thermostats these days and most run on battery power. Those batteries do have to be changed from time to time. My electronic thermostat supposedly had a low battery indicator, but I’ve found that changing the batteries before seeing the indicator has helped in the past. An electronic thermostat is just an automatic switch that basically turns your AC unit on and off at certain temperatures. If the batteries are low the switch may not be turning on or reading the air temperature properly.
3. Check your air conditioner’s fuses and circuit breakers: A central air conditioner may have several different fuses in the whole electrical system. First try resetting the fuse for your central air conditioner at your electrical box by turning it off and then on. For my system I have to then go to my furnace/blower and flick a second switch on and off. This switch turns off whenever I turn off the main electric to it. A third fuse is probably outside on the wall next to the air conditioner unit or on the unit itself. Unless you know what you’re doing I wouldn’t recommend trying to change out these fuses which are often not on switches from what I’ve seen.
4. Check any AC reset buttons: Some newer air conditioner units have reset buttons which are essentially just fuses as well.
5. Wait 15 Minutes: This sounds silly, but after a recent power outtage from a thunderstorm we found that our central AC wasn’t kicking on. Our electronic thermostat was blinking “Cool On” which meant that the thermostat was, in theory, working, but the AC wasn’t responding. I went through the house resetting circuit breakers, hitting the reset button and doing just about everything I could think of. Finally, I just turned everything off (shut off the fuse, turned off the AC on the thermostat) and just… waited. I purposely waited about 15 minutes because I remembered that some AC units purposely won’t power on for a certain amount of time after a circuit has been tripped. Me flicking the circuit breakers back and forth probably didn’t help. After the 15 minutes was up, I flipped the circuit breaker back on, went to the thermostat, crossed my fingers, and turned on the AC. It started running almost immediately!
6. Read your central air conditioner’s operations manual: I put this last because, let’s face it, you’ve probably lost or never had the operations manual! If you can find the operations manual to your central air conditioner unit you may want to investigate to see if there are any recommended troubleshooting suggestions. By the way, if you know the brand and model of your central air conditioner you may actually be able to find a copy of the manual online. The same is true if you’re not sure of how your electronic thermostat works.
If you’ve tried most of these and still can’t get your AC working then the problem could be less of an electrical one and more of a mechanical one. Remember: be safe! If you’re uncomfortable trying any of these steps then call a qualified air conditioner repair person!
From what I’ve seen most central air conditioners have a lifespan of about 12 – 18 years, though I once lived in a house with a little unit that was 22 years old and still running well. Though it might cost you $2,500 – $5,000 to replace it’s important to remember that a new one will be much more energy efficient than your old unit and you’ll have a little more peace of mind when you see those triple digits pop up on the weekly weather forecast!
Good luck and stay cool!
Comment by David Shifflett
thanks for the great info keep it up
Comment by angela dempsey
I just bought a ac digital thermostat and it did not last a week can someone tell me what to suggest or look for from the ac man this thermostat repair cost me $308?
Comment by Tamara
I had tried everything I could think of to fix my temperamental AC. After reading this I changed the batteries in my thermostat and I have AIR again. Beautiful cold air! Whoever wrote this is my hero of the day!
Comment by Tom
Glad I could help! I mentioned the battery trick specifically because I’ve had the same problem with my electronic thermostat in the past!
Comment by rav
WOW! Just spent two hours trying to fix my home A/C unit. Wish I had found your post earlier…battery changes fixed the problem. COLD AIR !!! =D
Comment by joyce kearns
I HAVE ADIGITAL THERMOSTAT THE TEMPERTURE SETTING KEEP CHANGING. DO I NEED A NEW ONE
Comment by Tom
Joyce, you might need a new electronic thermostat, but more than likely your electronic thermostat came with a pre-set schedule that’s designed to save energy. Most electronic thermostats allow you to have four preset times during the day.. My electronic thermostat’s default schedule will allow my home to get much warmer during the middle of the weekday because it figures I’m at work. Around 5pm the default temperature is a little lower because it figures someone will be home. You should check the instructions for your thermostat. I’m guessing that the schedule got knocked out of wack or was never set properly. That can sometimes happen when you switch batteries in an electronic thermostat. Good luck!
Comment by Suzanne
My AC thermostat is showing one or two stars (**) next to the temperature. Could this be due to a dirty filter? Do i need to call for maintenance or is there something i could do first? The unit is only 5 years old.
Comment by Tom
Suzanne, have you ever replaced your AC filter? It should be done at least several times a year, especially if you also have forced hot air heat. You might want to try replacing that before calling someone in. Try to find your thermostat’s manual to see exactly what those little stars might mean. You can actually find most electronic thermostat manuals online now as long as you know the brand.
Comment by Stan
Those are great tips but having your unit regularly serviced is good to do. They can often find problem that are starting before they become an expensive issue.
Comment by Irwin
My unit outside my house doesn’t come on when the AC is turned on. My thermostat is set to cool and to automatic. The temp is set at 64 degrees but it doesn’t cool off in the house. The unit outside doesn’t come on can you help?
Comment by Tom
Irwin,
Try some of the steps above. It could be a fuse or switch you’re unaware of. If you’re really stuck then it might be a good idea to call your utility company (some offer affordable service plans) or a company specializing in Air Conditioners and Heating issues. They’re used to getting a lot of business when the weather gets warmer, and some might even be running some specials or deals. Good luck! Let us know what the problem with the AC is if you find out!
Comment by christine
I have the same problem as Irwin. I am wondering what is wrong with his system when the condenser blade is not rotating.
Comment by danielle keefe
My air condiotioner works but is not blowing. What can i do?
Comment by Larry
I set my thermostat between 74-76 during the day (I live in Texas average high right now is 95). the A/C runs all day long and in the late afternoon the inside temp is 82. If I turned the a/c down in the 60′s I would still have the same inside temp. Any suggestions?
Comment by Leathea
helpppp! My ac stop working last night I have a up payne unit ,but the digital therm is a carrier and it not lighting up at all tried to change the circ breaker and thats not it turned all the whole house power and still nonthing its hot down here in GA can someone tell me what to do.
Thanks the Hotone
Comment by Tom
If you AC condenser outside is running but the air in your house is not being blown out of the vents, then it could be that your air conditioner’s fan isn’t working. Some have fuses, some just “wear out” over time.
The different brands of programmable thermostats should work with just about any brand of air conditioner, so brand alone shouldn’t be an issue.
Another possibility is that something in the electronics of the controller board has gone bad. If you try all the basic steps of getting your AC working and you still aren’t getting any results then you’ll probably want to call in a heating and cooling professional. It’s difficult to troubleshoot air conditioners or heating units without being able to see or test the unit you’re working on.
Comment by Emily from AbleAir-1
Tom, great article for homeowners! Another point is that if you do need to upgrade your air conditioning system, this is the year to do it! The federal government is offering a $1,500 tax credit good for 2010 only, for upgrading to a more efficient model (see energystar.gov). For more info on saving money with your AC this summer, check out my recent blog post, and feel free to use any of my tips for your blog and readers! The more we share, the better! http://ableair1.sites.captico.com/2010/06/22/5-easy-ways-to-lower-your-air-conditioning-bills/
Comment by Leathea
Thanks for the info but I got it fix and the prob was the fuse in the furnace how bout that!!yay got air now.
Comment by gina fox
HI, my airconditioner comes on whenever it wants to. right now it is workinig but in an hour it wont..most of the day it doesn’t turn on. i did get a new thermostat..didnt help. changed batteries and turned on and off all the switches i possible could find…can anyone tell me what the problem is?
thank you …
Comment by Tom
Gina,
For an AC that comes on sometimes but not other times is difficult (but not impossible) to diagnose. There is a chance that there’s a loose connection somewhere and the vibration of the fan or just people walking around in the house is enough to knock something loose enough that it’s blocking the ability for the air conditioner to work as it should.
I had a similar problem with my brand new air conditioner unit for about three months. It would run great for 4 days and then, bam, it wouldn’t turn on. I would reset everything, poke around inside and, almost magically, it would start working again.
The final culprit? Something (to this day no one knows what) was loose on the main control board. I had the same guys who installed the AC come out and look at it three times over. On the third time the guy was stumped (he actually witnessed it cutting out) so he went down and literally took the entire control board out, re-seated everything he could, tighten the wires and nuts and reinstalled everything. Presto! Two years have passed without a problem (knock on wood!)…
Bottom line: it’s probably not going to be an easy diagnosis. Sorry. Sporadic problems rarely are. If anyone else has any suggestions, please leave them here!
Comment by Heather
I had my a/c put in last May and it worked last year just perfectly (great since it hit 108!). Then when it was time for the heater to be used, it kept tripping the thermostat so they came and fixed that. Now that a/c is needed, the outside unit will not come on. The furnace is running, the inside circuit breaker is fine so I’m assuming it’s the outside one but of course, that’s one that I can’t deal with myself, right? And they can’t come out until Tuesday, which will be cool enough not to need it. It’s infuriating that this happens after only a year. My folks and friends have never had any issues with their units.
Comment by frank
my ac unit doesn’t get cool enough but runs all the time and the temp is set at 72degrees but the temp out side is 86 degrees it also seems like it putting moister in the air
Comment by Sandieg
First, thanks for all the hints! Got up this morning in hot, sunny Florida and no AC. I noticed the digital thermostat was not lit up, replaced the
batteries…still did not light up. I reset the breakers…still no thermostat light. Turned it from auto/cool, to on/fan…nothing. My filters were just changed, so that’s not it. Will try resetting the main breaker and my son is searching for a reset button on the compressor. Our power company just got a 40% rate increase…bills so high, can’t afford a
repairman. Anyone know why the thermostat won’t light up, with newly installed batteries? It is 76 degrees in here this AM, but by noon, it will be 96 degrees without AC…help! Thanks!
Comment by Sumir
Last night my outside AC unit was making unusually making high noise. Later, I checked the blowing air from duct. It was not cold as it should have been. I shut the AC off for the night thinking something is not right with outside unit. In the morning, turned AC ON. Inside blower fan came ON and flowed air. Outside unit made slight noise, but did not see FAN running. Immediately, turned the AC OFF and kept it off.
This AC has been working quietly so far. Have had no problem. Every year, I clean up outside unit and prepare for the season. So, it appears that last night outside fan may have stopped working and that is why outside unit was making unusual noise. Is that the FAN that is gone? How do I find out where the problem is? Any help is appreciated.
Comment by arnold
The AC is not cooling inside the house at the set temp. I had a technician recharge the freon, check all component functionalities. Apparently, my guess the system is not pulling out the hot air inside to balance out the incoming cold air. So any suggestions.
Arnold
Comment by Joshua
Tom, I had a new Trane outside unit and new inside coil installed in April. I set my thermostat to 78. It happened three times in the past month that the room temp rose to 84. The outside unit stopped running but the inside fan was still on and blowing air. The air that it blew out was not cool air.
I called my A/C guy and he said it could be a bad battery on my thermostat, so I changed it but it still happened again. He said it could be the breaker circuit. How can I tell?
I had two thermostats. One is electonic one that I replaced in a year or two. Another one is an old basic Honeywell thermostat. Do you think the old one creates the trouble? I tends to set the electronic one to 78 and the old one to 80 because the old one is in the second floor game room that no one is going there. Thanks
Comment by Steve
my air condition is coming out of the vents great in most of the house but in my family room the air isnt as cold and isnt strong? what should i do?
Comment by Jeanette
My AC unit is receiving power but it isnot kicking on. I have tried to chnag the batteries in the thermostat. Tried the fuses and tried the reset switch and still nothing please help.
Comment by Tom
Wow… lots of questions… AC issues are always difficult to diagnose because there are a lot of different variables and parts that all have to work together. Unfortunately, not everything is easily fixable by the homeowner and some states actually limit what homeowners are allowed to fix (as much as they can) for safety reasons.
If your AC is running but your home isn’t getting as cool as you think it should, then you might want to think about having a service person “charge” your air conditioner with freon or another coolant. This isn’t a terribly difficult procedure, but it requires special tools and needs to generally be done by a professional. The air conditioner works by moving warm out of your home through a coolant and then bringing cooled liquid back in (that cool air then blows through your home). If you have a little leak or maybe the amount of coolant has just slowly depleted over the years then, yeah, your AC may not cool your home as it should and may just run forever without doing much good.
Second consider humidity. When it’s very hot and humid out there’s a chance your AC just can’t keep up with things. More insulation, newer windows and doors and general energy efficiency will help, but those are all expensive and somewhat long-term solutions. Try drawing the shades in the warmer rooms… Here are more tips for lowering your electric bill in the summer. I have been in million-dollar homes that have a hard time staying cool on unusually hot and humid days, and even more so if you have a whole week of that sort of weather. One other option: consider a dehumidifier for humidity. That’s part of the principal behind an air conditioner: it helps draw moisture out of the air to make cooler….
Dog urine ruining an outside air conditioner unit? It’s actually possible if the dog kept urinating in the same spot. Animal urine is fairly acidic and over time I’ve seen it pit and rust right through metal.
If your thermostat isn’t lighting up it’s possible that the bulb is out, but the newer ones use LEDs (which don’t burn out)… You could have a loose wire or cobweb somewhere that’s shorting something out, unfortunately. It’s difficult to diagnose…
Electronic and old manual thermostats can go bad. It isn’t unheard of. They’re not difficult to replace, but if you’re not handy it might be better to call in a professional. If you do call a professional, here’s a tip: buy your thermostat from the store yourself and only pay the pros to install the one you bought. Most shouldn’t give you a hard time about it and you’ll save a fair bit of money.
I did write up an electronic thermostat guide you can check out if you’re looking for more information. Remember to read the manual! If any of these suggestions or solutions work, please let us all know here!
Comment by annette
I have an a/c-heatpump and when the thermostat reaching the desired temp I have it set for, it will kick the breaker.. I have to go reset all 3 breakers and then turn the thermostat from auto to ON and it will come back on and cool.. It will run for hours like this (fan ON) but when the temp reaches that temp it will kick the breaker again.. **when it trips the breaker the inside fan continues to blow, it just isn’t cool air and the outside unit is not working) Also there is 3 sets of double breakers and 2 of them are labeled furnace 1 set green, 1 set orange, but on the other side there is 1 set of orange that isn’t labeled but that is the one that keeps tripping and turning off outside unit… Could this be the thermostat? Thanks for all your help in advance..
Comment by Espe
same problem that Arnold my unit is new, what is the correct difference between the set up temperature in thermostat and the cold air that goes to the air ducks? any comments…
Comment by zulfi burki
whether this works or not. thank you for posting a solution. i have a feeling all i need to do is the waiting part now. so ill see what happens in about ten more minutes. thanks!
Comment by Scott
My brother’s central air unit will run perfectly most of the time. But, for some reason, it just quits mid-day and he has to go and turn it off at the thermostat, shuts of the main breaker, and waits a few minutes, turns the breaker back on, and it will run again. Sometimes he does this 2-3 times to get it running, but does eventually start running again. Any idea of the cause???
Comment by RJ Lewis
Here’s a tip. My sister recently cleaned/replaced her filters. Her AC worked for about a day, then stopped. It turns out that when you replace the filter cover, the screws have to be put in just right to make a perfect seal and also push against a tab that makes a closed circuit. If you recently replaced/cleaned your filters, make sure they are set correctly and your cover is back in place just right. In her case, it was initially connecting, but the vibrations over about a 12 hours caused it to loosen.
Comment by Jennifer Larsen
Just got mine fixed for $119 for something very simple.
Our central air stopped working (and the fan, as well) Apparently, most systems have a ‘kill switch’ that shuts it off if the door panel is taken off of the back of the heating/air unit in the house. He secured the door panel which pushed in the botton and voila’. Wish that had appeared on one of these blogs….
Comment by Tom
Thanks for all the AC help! Yes! I’ve actually had the vibration problem, too! When my AC was first installed it would kick out every day or so, which was driving me and the installation guys nuts. Eventually the HVAC tech found that there was a little switch that was loose on the main circuit board and he figured the vibrations from running was just enough to trip it every so often. He actually tighten the switch on the board and everything worked great from that point forward.
I’ve also had a bad breaker (in the outside box) that was causing problems. It would seem to trip if it got too humid outside. I actually had an electrician come in and look the whole system over. We ended up replacing the breaker and everything worked well.
Comment by Gina Gelvero
Have a nice day! Could you please help me how to solve the problem of my A/C since 3 days days now its not working well not cold and I have cleaned already the filter, what are the other reason why its not cold???
Pls. Help! ! !
Thanks a lot.
Comment by Khamika Cooper
My A/C wasn’t blowing yester seems to have went out after the storm. When I went to look in the back it was like a bit of ice on the back but the fan was blowing, no air was coming through the vents. So I turned it off for a day and turned it on today it’s pushing air up now, I just turned it on. Is there a problem with it, or was it maybe the storm.
Comment by darren
great advice did all trouble shooting went to home depot and got fuse tested free and purchance new fuse they were not working got air thanks again and keep up the great work
Comment by gregg
i woke up this morning and my blade on my outside unit wasnt spinning but everything inside was working perfect. after turning my unit on and off a few times my outside blade starting spinning again. now for some reason my air isnt getting cold but everyhing seems to be working the way it should.does anyone know why my bade wold of stopped spinning or can anyone just help me. ive cleaned it and everything else i can think of but still warm air. thanks