Why Is My Air Conditioner Not Cooling the House? 11 Common AC Problems Homeowners Face

Over three-quarters of all homes in the US have air conditioners. That makes ACs some of the most popular equipment around the country.

There’s a good reason why homeowners spend a significant amount of money on efficient air conditioning. The sweltering heat of the summer can be unbearable. A reliable AC keeps your indoors comfortable.

But have you ever turned your AC on and suddenly wondered, “Why is my air conditioner not cooling the house?” It can happen without warning, and sometimes it isn’t easy to pinpoint why.

Understanding some of the most common AC problems can keep you better prepared when they eventually strike. In this comprehensive guide, we outline 11 likely culprits for your air conditioner not cooling.

1. The Filters Are Clogged

Perhaps the most common cause of AC issues is clogged filters. Dirt, pet hair, pollen and dust can clog your filters.

When filters get clogged, they begin to restrict the flow of air through your AC. The result is that the AC doesn’t cool your indoor air effectively. Clogged filters can also interfere with the functioning of your system’s indoor evaporator coil and outdoor condenser unit.

The best way to avoid issues with clogged filters is to clean them regularly and change them when required. We recommend changing them every three months. For those with pets, it may be necessary to change filters more often.

2. The Refrigerant Is Leaking or Low

AC systems use refrigerant, a chemical that transfers heat from the indoor space and moves it outdoors. There are many types of refrigerant, including Puron and the well-known, phased out Freon, that cool the air in your AC system. When the refrigerant level is low, your AC may have problems cooling the air in your home.

There are two possible reasons your AC’s refrigerant level is too low. It could be that the system was undercharged during installation.

More commonly, it could also be that there’s a leak within the system. In such a case, it’s important that you seek professional AC repair right away. A refrigerant leak can cause refrigerant poisoning, although rare, and harm the environment.

3. The Coils Are Frozen or Dirty

While your AC’s filters do a great job when it comes to keeping the evaporator coil clean, the coil can also experience problems over time. (Incidentally, installing a UV light can help reduce the gunk that builds up in the indoor evaporator coil. It also improves air quality.)

Coils tend to get dirty over time because they stay humid and it’s easy for mildew and mold to build up. This can adversely affect their functioning. Coils can also freeze over and stop working, particularly when there’s not enough refrigerant in the system.

4. There’s Leaking Air

Have you had pests in your attic recently? Many homeowners find that squirrels, rats and other critters have taken up residence in their attic and damaged the duct work.

Damage can also be caused by improper installation of duct work that deteriorates over time.

We also hear about plumbers, cable providers and other home repair technicians who accidentally damage duct work in the attic.

These reasons are what most commonly cause air leaks leading to a hot home. Air ducts distribute the conditioned air throughout your home. If they have leaks, it will reduce the cooling in your home.

5. The Compressor Is Not Running

Your AC’s compressor is the heart of the entire system. The compressor circulates refrigerant between the indoor and the outdoor units. When the compressor gets damaged, the entire system can’t cool your indoor air effectively.

Other smaller and less expensive electrical parts may have gone bad which can look like a compressor failure. For example, you may need to replace the capacitor or other hard-start device which keeps the compressor going.

If your system is equipped with a ceiling saver device (or float switch), it will also turn off your compressor if your condensate drain has gotten clogged. This prevents water leaks in your home.

Problems with an AC’s compressor can best be solved by replacing it. The biggest problem is that compressors can be incredibly expensive. Unless you have a warranty on this part, you may want to replace the entire outdoor unit.

6. Problems with the Exterior Fan Motor Could Be the Culprit

Your AC’s outside fan within the condenser unit is responsible for taking hot air from your home and releasing it outside.

Unfortunately, the fan can develop problems and cause your AC’s compressor to overheat. The best solution for this problem is to get an expert in AC troubleshooting to fix it. If your fan motor goes bad, your fan won’t run and your air conditioner will overheat and shutdown within minutes.

7. There’s a Problem with the Thermostat

Your central air conditioning’s thermostat measures the temperature of your indoor air and adjusts it to your preference. When there’s a problem with your thermostat, it can lead to problems with your AC’s overall functioning. Occasionally, thermostats fail, and replacement is an easy solution.

Sometimes, the issue may be your thermostat’s settings. For example, make sure your thermostat is set to cool not set to heat.

If your thermostat requires batteries, replace them with new ones. Some of the newer smart thermostats can benefit from a hard restart. That is, remove the thermostat from its power source, then return it so it can reboot. If you touch your thermostat and it appears to be frozen, this can be a quick fix.

8. The Registers Are Dirty or Blocked

Your air conditioner’s registers can get dirty over time, just like the filters. This especially happens when you forget to clean registers regularly.

Sometimes they get blocked, which is very bad for air flow. Sometimes homeowners block them on purpose because they aren’t using a particular room or furniture gets placed in front of them by mistake.

Dirty or blocked registers force your AC to work much harder, increasing your energy bills without effectively keeping your home cool.

While this problem is among the most common AC issues, it’s relatively easy to address. Simply remove your AC’s registers and give them a good vacuuming to remove any debris or run them through the dishwasher. And, unblock any registers that  might have been closed.

9. Look Out for Excess Heat from Nearby Appliances

You’ve probably noticed how hot your TV, laptop, lamps, and other electrical appliances in your house can get.

Given that it’s your thermostat’s job to adjust and regulate the temperature in your living space, appliances that give off heat can affect your thermostat’s functioning when placed too close to the thermostat.

Always make sure there’s enough distance between the thermostat and electrical appliances that give off excess heat.

10. There’s Too Much Heat From the Sun

The main reason you invested in an AC system was to escape the sun’s heat. However, if the sun is shining on your AC’s thermostat, the extra heat can put the system in overdrive and cause problems.

During unusually hot days, it’s advisable to keep your shades drawn to reduce your home’s heat load.

11. You’ve Skimped on Proper Maintenance

A common reason for an AC system’s inability to provide cool air is poor maintenance.

Sure, you may keep the different parts of your AC clean. But you’ll still need to find the right HVAC company to give the system a thorough check-up. We recommend an AC tune-up twice a year, in the spring and fall.

During this tune-up, an AC technician inspects the parts of your AC that you can’t reach easily. The technician will be able to identify any potential problems and address them before they lead to expensive repairs.

Need Help with an Air Conditioner Not Cooling the House?

Hopefully, the next time you’re thinking, “Why is my air conditioner not cooling the house?” you’ll be able to pinpoint the problem quickly.

The good news is that many of these problems can be easily avoided or fixed. But if you’re not sure about how to troubleshoot the problem, it’s best to call a licensed AC technician for help.

Contact Rob and Kenny at Terry’s A/C & Heating at 281-495-7830 for prompt service and an expert HVAC repair. Since 1982, our family-owned HVAC company has been serving residential and light commercial customers in the Southwest Houston and surrounding communities of Richmond, Katy, Sugar Land, and Fulshear, Texas. We are a Carrier Factory Authorized Dealer, and we guarantee our work.