Why Isn’t my Central Air Conditioner Cooling?

I’ve lived in Kansas for over twenty years now and while I love it here I will have to say that the summers can be quite brutal. I’ve seen multiple weeks in a row where we have constant one-hundred degree heat in July and August. It nearly makes you sick when you step outside.

While hanging out in the pool is a good way to escape the heat it is not a long term solution and in some cases the water gets so hot that it’s not even enjoyable anymore. Most of us Kansans stay indoors where the air conditioning keeps us comfortable at a nice seventy-four degrees. But, what do you do when you come home after a long day only to find that your central air conditioner is no longer providing cold air.

Unfortunately, when this does happen there could be a variety of reasons and causes behind it. Some of these problems can be fixed by yourself even if you have little knowledge on how air conditioners work. Other problems though will require a professional HVAC service technician to come out to your home and troubleshoot.


Let’s hope that the problem you are having you are able to fix. In this section we’re going to take a look at some of the simpler fixes. Sometimes it is just easy, but don’t get your hopes up. You may end up facing a large repair bill.

Let’s start with the easy fix first. Have you checked your thermostat? Yes, it really could be that simple. In some cases homeowners have come home and realized that their thermostat was accidentally set to heat. (My toddler has done that before without me knowing… so don’t feel bad!)

If the thermostat is set to cool then another thing to check on your thermostat is the fan setting. Not all thermostats have this setting, but you should check yours if it has a ‘Fan’ option. Typically the fan option will have ‘Auto’ or ‘On.’ If the fan is set to ‘On,’ then that means you have the blower running constantly even when the air conditioner hasn’t kicked on. While this would account for warm air coming through your vents it would not account for a very hot home. (If it was just the fan then your house will still be somewhat cool.) Just to be safe though, I would set the fan to ‘Auto.’ When set to ‘Auto’ the fan will only come on when the air conditioner is on.

Another possible cause for the warm air blowing through your vents is an obstruction or restriction to the airflow of your system. In other words, something is blocking air flow and in most cases it is your air filter. This is the filter that you’re supposed to replace every few months. You did replace yours recently, right? If you didn’t, then this may be the cause of the warm air. Purchase yourself a new filter either at the store or online. If you are unsure what kind of filter to get check out our central air conditioner filter best of guide.

Along with swapping out the air filter inside your home you can also take a look at your outside system. How does it look? Is it covered in debris such as leaves, grass, and dirt? Are there shrubs or trees right up against it? In the case of the trees or shrubs I would either remove them or trim them back to give the air conditioner enough space. If the unit itself is looking quite dirty then you can take a garden hose on a LOW setting and gently spray the sides of the unit. When doing this ensure that you are only spraying the hose at the air conditioner’s condenser. (This is the side with the fins.) Do not spray on the top of the air conditioner. Also, be sure to turn your air conditioner off when spraying.

Service Call 

Well folks, we have exhausted what a homeowner can do to diagnose and fix their air conditioner that is blowing warm air. Now, we will take a look at what some of the other problems could be. While you may be tempted to try and correct some of these problems yourself I would recommend contacting a professional to ensure your safety and to also prevent you from further damaging your system.

A reason for blowing warm air that technicians come across a lot is that the outside unit isn’t receiving electricity. Remember, that you need both inside and outside units working together in order to achieve cold air and if your outside unit is no longer receiving electricity then that would explain your problem. You can check your circuit breaker to see if power is being routed to the outside unit. However, if you do notice that the circuit has been tripped or a fuse has blown then you should contact your service technician immediately. I repeat, do not try to fix yourself.

Another possible reason for your air conditioner not cooling is that the evaporator coils are dirty with dust and are having trouble absorbing heat. While it is not recommended you clean this yourself this could be causing your problem. If you schedule a yearly maintenance checkup on your air conditioner your service technician will clean these coils for you to ensure they are working in top condition. (You may have to ask for this service as not all techs will do this.) The good thing here is that if you are diligent on swapping your air filters every month or two then you will most likely not have dirty evaporator coils.

You could also be having problems with your duct work. It could be that some of your duct work has been broken or disconnected. Or, it could be that your ducts are actively leaking air. This isn’t as common of a problem, but it can happen. If not your duct work it could also be a faulty fan motor. Your fan motor is the motor that gives the power to the fan on your outdoors unit. This is the fan that expels the hot air from your home. (If you were to lean over your air conditioner while it’s on you’ll see the fan moving back and forth blowing the hot air away.)

While the above reasons can be causes as to why your air conditioner is not working they are not the most common problem that techs come across. No, the most common are the two problems listed below. The downside here is that these problems can be quite expensive to fix. Let’s take a look:

Low Refrigerant

If your system isn’t cooling your home or is blowing warm air then it is likely that it is low on refrigerant. Refrigerant is the ‘blood’ of your air conditioner. Without refrigerant your system cannot absorb the heat from your home. If you do have low refrigerant do NOT just add more refrigerant to your system. Refrigerant flows through your air conditioner in an endless cycle. In other words, you should never run out of refrigerant… unless you have a leak. If you, or your service tech, adds refrigerant to your system without fixing the leak then you are just throwing money out the door. You are going to have the same problem again when that new refrigerant leaks out.

Instead, your service tech needs to identify where the leak is coming from. Is it on the refrigerant lines going back and forth between the evaporator and the condenser? Is it in the outside unit? Or, in the inside? Once the leak has been determined the technician will patch it and then recharge your system. While the patch may not be too expensive the recharge of refrigerant can get quite pricey, especially if most of your refrigerant has already leaked out.

Also note that you may have more than one leak in your system. This can happen in the piping of older systems. Sometimes the old piping can get corroded and cause multiple micro fractures throughout the lines. In this case your service tech may need to replace the entire pipe.

Compressor Problems

The other most common problem with a central air conditioner is a bad compressor. If refrigerant is the ‘blood’ of your air conditioner then the compressor is the ‘heart.’ The compressor is what circulates the refrigerant throughout your system. If there is a problem with the compressor then it will most likely need to be replaced.

Unfortunately, a compressor replacement can be an expensive repair. It could be a couple hundred or it could be six or seven-hundred. It is hard to gauge this as there are other factors to consider. Such as what size is your air conditioner? Did the broken compressor cause other problems? Does the system need a recharge of refrigerant?

Yes, that’s right. In some cases you could have a faulty compressor and need a refrigerant recharge. If that is the case then I’m sorry to say that you’re going to have a hefty repair bill.


Here’s hoping that you do not have to face an expensive repair bill. But, if you do end up having to pay five-hundred or even a thousand dollar repair bill it may be time to ask yourself should I pay for the repairs or should I invest in an entirely new air conditioner?

The question to this answer depends on how old your AC is and how many problems you have had with it in the past. If the system is five or seven years old and has been moving right along without many issues then I would hold onto it and pay the repair.

However, if your system is ten or even fifteen years old and this is the third or fourth repair you’ve made in recent years then it may be time to consider scrapping it and purchasing a new system entirely. Yes, it is a lot of upfront cost but the upside here is that you’re throwing money down the drain every season when something else breaks on your current air conditioner. At least with a new system you get peace of mind and know that you aren’t going to have a problem for quite a while. You most likely will get a two or three year warranty as well with the purchase.

All that being said though, I have seen air conditioners last past twenty years. I was looking at a house the other day that had a split system that was twenty-two years old. It was still going strong too. The condenser looked terrible and was covered in rust… but it was still cooling. I don’t know how much money the owners had invested into that unit over the years so it’s hard to gauge.

It’s all a matter of perspective. Do you want to spend a bit of money each year and limp your air conditioner along, or do you want to purchase a new system and have peace of mind for the next five or so years. The choice is yours but I hope this article was helpful and pointed you in the right direction.