Paying a huge amount for an AC unit and then in summer if it doesn’t cool it can be quite frustrating. As an AC owner, you should know how to troubleshoot minor problems if your AC is not cooling.

I have been in this AC repair business for about 6 years now and I know what are the most common problems that can cause ac to not cool enough.

So In This article, I’ll explain 16 different problems to check If your AC is not cooling. In this way, if the problem is minor you can repair it yourself. 

Reason No #1: The Outside AC unit is not Running

The first reason why the air conditioner might not be keeping up is simply that the unit outside is not running at all.

So I've been to quite a few houses where the homeowner thought that the air conditioner has been running this whole time it's just not cooling enough.

Whereas the unit outside was not running at all it was just the fan circulating the air inside the house the fan that's in the air handler or the furnace.

So if an air conditioner is not cooling enough or not cooling properly a good place to start is to see if the outdoor unit is running at all. 

Reason No #2: Your AC Capacitor Is Dead

Reason number two why the ac is not cooling enough can be because of a dead capacitor. A lot of these air conditioners have a dual capacitor which means that it's basically two capacitors in one.

So the capacitor is almost like a battery for the fan and the compressor. So what sometimes happens is the compressor side of that capacitor dies but the fan is still alive.

So what that would look like is the fan of the outside unit is running. But the compressor that's actually pumping the refrigerant is not running, in that case, there’ll be no cooling at all.

It's almost like just having the fan inside running on its own. A bad capacitor is actually one of the most common ac problems. 

Click Here To Check Our Detailed Guide On How to Replace Your Capacitor At Home

Reason No #3: Your AC Compressor Is Locked Up

Reason number three is a locked-up compressor so it would look similar to that previous scenario that the fan might be running but the compressor is not turning on.

And the capacitor is good in that case but the compressor is locking up which means that it's trying to start but it's failing to start.

This happens more commonly in older units and many times you can actually get it going by putting in a hard start kit. Now if your compressor is already locking up chances are that the hard start kit will only prolong the life of the unit by a couple of years.

But the problem will probably return down the road. Although I have seen it prolongs its life by five or more years. 

Reason No #4: Your AC Condenser Fan Motor Has Gone Bad

Reason number four is a bad condenser fan motor sometimes this is obvious you come outside and the fan is simply not spinning.

But you can hear the compressor running and if you try to spin it with a stick or something you can tell that it's just really seized up. You could try oiling it to get it going that doesn't often work.

I mean if it's already locked up to the point where you're barely able to spin it oiling it is probably not going to help. So sometimes it's obvious where the motor is just completely seized up sometimes it'll even be steaming or if you put your hand on it it'll be super hot almost to the point of burning your hand.

But other times it's not as obvious sometimes I come out to a unit and everything is working fine the air conditioner is cooling the house good everything is good but the customer says that my temperature just never goes down to the setpoint some of those problems are really hard to track down because they're intermittent.

So what will happen is the motor is failing but it takes time for it to overheat so it can run for like a whole hour before the motor starts to overheat and you could actually see it slowly slow down and come to a stop.

So those can be pretty tricky to catch. Because after a while that fan motor will cool off and then the fan loader will usually come right back on.  

Reason No #5: Your AC Furnace Filter is Clogged/Dirty

Number five is a dirty furnace filter or the filter in your air handler. Now this problem is actually one of the most common ones as well.

Actually, I was just at my dad’s house and he tells me that his air conditioner doesn't seem to be keeping up, and right after he says that he himself realizes oh hey I don't think I changed my filter in a while.

So he goes down there to check it and he brings back the purple frame which is one of those premium filters that are already all sucked in and super dirty. So we put a new filter in there and within an hour we could already feel a big difference in the house so that's an easy thing to check.

If you haven't replaced your furnace filter in a while maybe try doing that especially if you're using the really premium expensive filters the ones where the accordions are closely knit together.

Those filters are great they filter stuff out very good but you can't forget to replace them because once they start getting dirty they become a lot more restrictive than those lower grade cheaper filters. 

Reason No #6: Your AC Evaporator Coil is Plugged Up

Reason number six is a dirty evaporator coil. The A-coil that sits on top of your furnace which is part of the air conditioner that does get plugged up and gets dirty.

Once that gets plugged up enough it starts to restrict the airflow which of course decreases how well it cools your house and if it gets plugged up enough that coil might start to freeze over.

So if you see any ice buildup that may be part of the problem unfortunately cleaning an a-coil usually is a pain in the butt. They're typically pretty hard to get to. You have to take apart the plenum the metal sheet that's around that coil. Sometimes you have to cut it open.

It's pretty rare but sometimes it'll have a door or it'll be positioned really nicely where you can get in there and just clean it with a vacuum and a brush.

But usually, it's not that nice for most people the best option is to call a duct cleaning company and just have them clean that a-coil.

Reason No #7: Your AC Condenser Coil Is Dirty 

Reason number seven is a dirty condenser coil that is located at the outside unit of the central AC. So what it does is it’s sucking air in from the sides and then exhausting it from the top right part.

Basically, the way it works is all the heat that it collects from inside the house it's going to be rejecting it from the top portion of the outside unit. If the coil is super dirty with grass dirt, cottonwood seeds, and whatever else.

Then that will, of course, restrict the airflow and cause the unit not to cool as well. So cleaning that is actually pretty easy all you need is some hose and water.

Most technicians will tell you that you have to spray it from inside out you have to take the top off or the fan off and spray inside out. But if that's hard to get off if there's like 20 screws.

I found that usually spraying it from outside in is more than enough on my unit. I typically just spray it from outside in and that gets the job done.

Reason No #8: Your Return Grill Is Dirty

Reason number eight is a dirty or plugged return grill and maybe the return duct sometimes. Most of the time I see that the whole return grill just taped off or blocked. Sometimes people have a box in front of it or something else blocking it.

Sometimes I see really hairy grills it's just covered with dust and many other things. So that's an easy thing to check for and clean.

If it's just the grill you can take it off and just wipe it down and vacuum it. And then as far as you can get try to vacuum that duct behind it as well.

Because usually, the dirtiest part of the return ducts is right by the grills. So if you can clean that area that should make a big difference by itself.

Reason No #9: Your AC Thermostat Is Bad or Malfunctioning

Reason number nine is a bad or malfunctioning thermostat. So sometimes the thermostat could be causing the no cooling issue.

Sometimes it shows you the wrong temperature or it doesn't turn the air conditioner on when it's supposed to.

Sometimes changing the batteries of your thermostat is all that's needed and if that doesn’t work then you have to replace the thermostat.

If it's not turning the unit on at all one way you can check is to simply bypass the thermostat. By taking it off the wall and putting a jumper wire between y and r to see if the air conditioner will turn on. Check Here How to bypass the thermostat and run your ac

Reason No #10: Your Thermostat Programming is Malfunctioning

Reason number 10 is that your programmable thermostat is messing with you. So if you have a programmable thermostat with a program in the background.

If you haven't programmed that or maybe you had a power outage and somehow the program got reset chances are that your program is messing with you.

So you adjust the temperature to let's say 72 but then when it comes to the next program cycle that can jump back up to 76 or whatever the temperature is on the program.

So if you have a programmable thermostat an easy way to get rid of all of that is to just put the thermostat on hold. And what that means is it will hold that temperature permanently it will not jump around. Most digital thermostats will have that hold feature.

Reason No #11: Your AC is Low On Refrigerant

Reason number 11 is that the AC unit is low on refrigerant. That's a pretty bad problem to have. This is not something that a homeowner can fix themselves.

So if the unit is low on refrigerant this is not something that should be refilled every couple of years. The air conditioner is a permanently sealed system which means whatever refrigerant or freon is in there should stay in there for life whether it be 20 or 30 years.

If you're adding refrigerant to it every year that means your unit does have a leak. Now there are two things that a homeowner can try to check themselves to see if potentially he has a problem with refrigerant.

One is to look at the suction line that's going to be the thicker copper line going to the unit. On a properly charged air conditioner while it's running that suction line is going to be sweating or condensing you should see little water droplets on it.

If it's frozen or dry then that could mean that your unit is low on refrigerant. Another easy check is to check the temperatures in your returned and supply ducts and see what kind of a temperature difference you have between the two it should be between 15 and 20 degrees.

Reason No #12: You Have A Leak in the Duct

Reason number 12 is a leak in the ductwork. So sometimes there will be a crack in the ductwork which can cause not cooling. So inspecting all your ducts or at least everything that you can see and get to is not a bad idea either.

Reason No #13: You Have An Undersized AC Unit

Reason number 13 is an undersized unit. Sometimes people buy big houses and they get a small undersized ac unit which is not enough to cool the whole house.

You can choose the correct ac unit for your house with the table given below.

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Reason No #14: Your HRV Exchanger is Running All The Time

Reason number 14 is that the air to air exchanger is running all the time. Air to air exchangers should be off during the summer.

So what the air to air exchanger does is it brings the outside fresh air to your home and takes the stale home air outside. So In summer, it brings the hot air from the outside and that can make your home very hot. So it’s better to keep it off in the summers.     

Reason No #15: You Have Open Windows

Reason number 15 is some windows are open inside the house. Now for most people, this is common sense. But there are people out there that think that it's okay to have windows open while your air conditioner is running that kind of defeats the purpose.

Because hot air travels from hot to cold so the hot air outside it's almost like it's getting sucked into the house. So long story short when the ac is running all the windows in the house should be closed.

Reason No #16: You Have a Bad Damper Motors

Reason number 16 is broken dampers motors or the whole zone control is malfunctioning. If you have a zone system that means that you're going to have multiple thermostats.

Those zones are controlled by motorized dampers that open and close on their own. Sometimes those dampers can break or the motors can break and that will fail to open. You can just call a technician and get that damper motor repaired.