Air Conditioner Won't Cool?  Some Troubleshooting Tips

Air Conditioner Won't Cool? Some Troubleshooting Tips

Asking an air conditioning guy why your air conditioner won’t cool is kind of like asking a mechanic why your car won’t run – there are a million reasons.  Since we are asked this question so often though, we do have a few good answers ready to go.  So when asked about “why an air conditioner won’t cool,” or “why an air conditioner won’t cool below 80,” the short answer is that you’ll have to call up your local HVAC technician if you want it done right.  But then, you’re not on the internet looking this up because you want to drop a few hundred bucks to call one of us out there, now are you?  If you are a return reader to the ASM air conditioning blog, then you know that we are a small, U.S. Veteran-Owned business in Southern California, and like to keep it honest, simple and efficient.  In this article, we will discuss the most common causes for why an air conditioner won’t cool your house properly, including the do-it-yourself troubleshooting tips you can use to get your AC unit up and running properly.


DIY Troubleshooting When Your Air Conditioner Won’t Cool

With any troubleshooting method, it is important to first understand that safety comes first.  Know your limitations – don’t go poking your head into an attic if you’ve never crawled in an attic before, don’t mess with electricity if you don’t know what you’re doing, and if you have any doubts at any time about what you are doing or whether or not you should be doing it, the answer is “no you shouldn’t.”  Call the professional out – it’s just not worth it, trust me.  I can’t tell you the hours I’ve spent in an attic trying to figure out what someone was thinking when they did something to their unit.  Fortunately, the most common causes for when an air conditioner won’t cool are pretty simple.

You may also be interested in:

AC won't cool troubleshooting graph

1. Check Your Thermostat

If you’ve checked our blog before, then you know that this isn’t the first time I’ve said this – the simplest answer is usually the right answer.  Without going on a tangent about Occam’s Razor, trust me when I tell you that you’d be surprised at how often I get called out to a house only to find out that it was, in fact, the wife that kept turning the thermostat up.  I am far from a marriage expert, as my wife can attest to, but please ask your significant other before you call us out…then make sure that your thermostat has power, is on, is set to auto and displays the desired temperature setting.

air conditioner won't cool houseAlso take note of your thermostat’s position in your house.  Whether you realize it or not, an air conditioner that won’t cool might not end up being the AC unit at all.  Your air conditioner doesn’t kick on because it thinks you are hot, and it doesn’t kick on because it’s hot in your house either – it kicks on when your thermostat gets hot and crosses whatever threshold temperature you have set.  In other words, check the location of your thermostat.  If your thermostat is in the deep dark hallway that is always cool and it is set to 72, then that doesn’t mean your house will be 72 in the front living room with the big windows that get sun all day.  Make sense?  Try adjusting your thermostat to start with, then read:

2. Next, Check Your Air Conditioner’s Air Filter

Sit in your chair, relax and take a few deep breaths.  Feel good?  Having any trouble breathing?  Probably not.  Now, take the down comforter out of the closet and wrap it around your face and take a few deep breaths (disclaimer: don’t really).  Is it easier or harder for you to breathe?  Now translate this to why your air conditioner won’t cool – maybe it’s cooling, but it’s having trouble pushing air into your house.  I say this in almost every one of our articles – your air conditioning filter isn’t really for you, it is a filter to keep contaminants from building up on your AC’s internal components.  The fact that it reduces allergens is just an ancillary benefit.  If you aren’t doing so, change your air conditioning filter no less than once every three months.  It may seem like a pain, or expensive, but your air conditioner works significantly harder when it has to push air through a saturated filter, just like you had to breathe harder through that down comforter.  So hard in fact, that this might be why your air conditioner won’t cool below 80 degrees in your house.  Change the filter and give it a try, then read:

3. Air Conditioner Still Won’t Cool Your House?  Check Your Circuit Breakers

Check the circuit breakers on your main power distribution panel (aka, your circuit breaker box).  Reset all air conditioner related breakers, including ones that are listed as “condenser,” “compressor,” “AC,” “Air Conditioning” and “HVAC.”  People often times mess this part up – some circuit breakers won’t actually move to the “off” position if tripped.  So to reset them, move the circuit breaker to the “off” position, wait a second, then switch it back to “on.”  Do this for all of the applicable breakers.

Next, go to the air conditioner itself (if it is on the roof, careful of loose leaves, etc. and don’t go up unless you know what you are doing).  If you have a “package” AC unit, then there is only one component, usually on the roof.  If you have a “split” AC unit then you have one piece outside and one inside.  Go to both and look carefully for another set of circuit breakers.  Some models have them, and some don’t.  If you see them, reset those too.  If one of these circuit breakers throughout this process keeps tripping off (making an obvious sound), then read: Air Conditioner Circuit Breaker Keeps Tripping for more information on troubleshooting this malfunction.  Don’t just keep resetting it!

air conditioner won't cool - condenser4. Check Your Air Conditioner Condenser

If you have a split unit (see: What is a Split Air Conditioner?), then the condensing unit (or “condenser”) is the piece that’s locked outside.  For a package unit, it is all together in one unit outside (hence, “package”).  Either way, go to it.  Check it for debris.  Any leaves, branches, dirt mold and grime that have collected on it needs to be removed.  WARNING – don’t stick your hands inside that thing yet because it could kick on and hurt you!  Either call a professional HVAC specialist, or for the veteran do-it-yourself types, start by removing power from the unit using two different methods (use both, not just one): turn the thermostat to the “off” position, AND turn off the applicable circuit breakers (in HVAC, we ALWAYS turn a unit off at two separate locations for safety – that way, when someone comes along and says “oh, the thermostat is off” and turns it on while your arm is elbow deep in your condenser…get the point?).  Another word for the wise is to turn off all the power, not just the air conditioning breakers.  Who said that whoever labeled those circuit breakers did it right?  In my experience, it’s about a 50-50 chance that it was labeled right – be safe and just turn off all the power why you do this.  After you turn them off, wait a few minutes just to make sure it doesn’t kick on, then go to work.

Ok, enough motherly guidance.  Remove all large pieces of debris, then clean the heck out of that thing with a hose and a brush.  These coils are the exact location that your air conditioner releases the heat from inside your house into the outside air, so make sure they’re cleaned well.  Replace all safety panels, etc., and turn the power back on, as well as the thermostat.

See if your air conditioner cools your house now.  If it doesn’t then you’re out of luck.  It is time to call the HVAC pros out.  If you live in Southern California, we ask that you keep us at ASM in mind, but chances are that you don’t live here.  Either way, here is an article I wrote on How to Choose a Reputable HVAC Contractor.


Excerpt Page 3 of 12 from the HVAC Design & Consultation Program Report

Click to Enlarge – Excerpt Page 3 of 12 from the HVAC Design & Consultation Program


Don't Overpay for a New Air Conditioner:

Hopefully, we were able to nip your AC problem in the bud.  If we weren’t, however, and you do need to buy a new air conditioner, then make sure that you aren’t taken advantage of.  Here’s how to get a fair price:




What to Expect From Your HVAC Technician

Like I said about the mechanic and your car at the beginning of this article, there are a million reasons that your air conditioner won’t cool, but you’ve honestly done everything that you can.  The number one thing that you can expect your air conditioning technician to do is to hook up to your system and check the refrigerant levels (either R-22 or R-410).  If he notices that they are low, he might opt for a Nitrogen Leak Check, where he will pressurize your system with nitrogen and wait for a while.  Then when he checks the gauge later he can tell if some nitrogen has leaked out.  If so, you have a leak and can go from there.  If not, then your Freon was probably just low.  He’ll top off your refrigerant and go from there.  Either way, call in the pro and see where it goes.

Final Thoughts When an Air Conditioner Won’t Cool

I hope this has helped.  In the end, when your air conditioner won’t cool it can be frustrating, but it isn’t then end of the world.  Follow the troubleshooting steps above and go from there.  At the end of the day, you might just need to call in an HVAC professional.  If something your contractor is telling you doesnt sound quite right or seems expensive, consider using our Online Consultation Services.  If you live in Santa Clarita or the Greater Los Angeles area, click the link below this paragraph to see if you are in our service area, and make sure to take a look at our ASM Air Conditioning Blog for more information and DIY tips.


Svg Vector Icons :
Timothy Kautz
About the author
Tim K.

The University of Virginia - 2005 / The Wharton School of Finance - 2016 / U.S. Naval Aviator 2005-2015. At All Systems Mechanical air conditioning and heating, we believe that the experience our clients have is every bit as important as the products they receive. Simply put, our results speak for themselves, and we'd be happy to help. If you're in the market for a new AC or furnace, make sure that you get a fair price! Try our online calculator; click the tab on the top of this page for more information.

Best Local HVAC Savings

Top 10 Brands
Repair or Tune-ups
Energy Efficiency
Contractor Prices

We Can Help You!

Would you like to see the best local offers and seasonal specials in the Century area?

Would you like to add any additional notes to your request?



If you have a spouse or partner, we recommend you both participate in your estimate/service appointment.

We want to make sure everyone's questions are answered.

Local request for new heater.

We value your privacy. By submitting this form, you consent to receive a call, email, or text from a specialist who may utilize auto-dial technology to contact you, even if the number you provided is on a do not call registry. Your consent is not a condition to purchase any product or service. Your specialist will listen to you, understand your current situation, and provide your consultation at no obligation.

Thank you. We've received your request.

A representative from NextGen Air (BBB A+ rated) will be calling you shortly to confirm your appointment. For immediate assistance you may call (855) 715-4500.

Limited time specials:

  • $68 Complete A/C System Tune Up
  • System/Replacement as low as $5995
(855) 715-4500 - 7 days a week

What Should You Pay for HVAC in your area?