Why is My Air Conditioner Running But Not Cooling the House?

Why is My Air Conditioner Running But Not Cooling the House? This is a questions I often hear when I was an HVAC technician. It is a very common question without a simple solution until I drill down more to find out specifics. There are many reasons why an AC is running but not cooling the home.

The problems could be in your evaporator coil, air handler, thermostat, air filter, or with another critical system component. Here are some of the typical follow up questions that I have for them before I can answer what really happened:

Is your air conditioner a central system or a window system?

This will let me know the complexity of the system and potential points of failure.

When you turn the switch on the AC, does anything happen at all?

  • NO:  Check the Circuit Breaker to see if the system is getting any power.  It that doesn’t fix it, then I’ll be focusing on electrical issues as opposed to mechanical issues.
  • Yes:  Most times this means that the unit is blowing, but not cooling.

Is the Thermostat turned all the way down?

  • NO:  Sometimes (especially at the beginning of the season) thermostats are still set for winter heating temperatures and just need to be adjusted.
  • Yes: Now I’ll be focusing on mechanical issues with the compressor and refrigerant levels.

There are a whole bunch of other scenarios, but this covers the vast majority of the situations that I encounter.  At this point, there is not much left that a typical homeowner can do other than to call out an HVAC professional.

I’ve had people call and say “My air conditioner is not cooling, can you come out and fill it up with coolant?”  Now I know of a lot of HVAC professionals in the business that would just say “Yeah, I’ll take care of that this afternoon” then show up and squirt some coolant in and take their fee. But what is really happening is that they are throwing a quick fit at a bigger problem.

Air conditioners should never lose coolant.  It is a closed system.  If the coolant level is low, it is because there is a leak in the system and that is the real problem that should be addressed by a professional.  Also, the fact that an air conditioner is running but not cooling as expected is not always the result of the coolant level being low. And adding more coolant to the system could damage it.

Reasons an Air Conditioner Running but Not Cooling

I’ll summarize a few things you should check before calling an HVAC professional when your air conditioner running but not cooling the house.

Thermostat Is Set Incorrectly

When your air conditioner running but not cooling the house, first check the thermostat settings. Be sure it is set to cool.

Dirty Air Filter

Dirty air filter can restrict the flow of air through your AC and reduce cooling to your home. Over time and without proper cleaning, air filters can become clogged. The best way to avoid issues with clogged air filters is to clean them regularly and change them when required.

Dirty or Frozen Evaporator Coils

If your air conditioner is turning on but not cooling, you might have dirty evaporator coils. If your evaporator coil is too dirty, this can prevent the amount of heat it can absorb, causing the cold evaporator to freeze over and disrupt the cooling process.

Refrigerant Leak

When there’s a leak in the refrigerant, some of the fluid is lost during the cooling process, resulting in a limited amount of cool air being produced.

Incorrectly Sized AC Unit

Remember that your Air Conditioning system should be sized to keep your home cool and comfort on the summer day. If your air conditioner is on but not cooling your home, you may have an unit that’s not sized properly for your home.

As you can see, there are several reason when you find your air conditioner is running but not cooling properly. You can check the thermostat, clean the air filter, and clean your unit as well. But if none of those options work you might have a bigger problems, in which case you’ll want to call in air conditioning services.

The dirty little secret in the air conditioning business is that most professionals are good at installing new systems (because that’s where the money is), but very few have enough knowledge to diagnose and repair an existing system.  When looking for someone to do air conditioning repair and maintenance, your best bet is to find them through our references. Get quotes from up to 4 different qualified and pre-screened contractors who service your area.

About Mas Broto

Have been in the heating and air conditioning (HVAC) industry for over 20 years. He is person that will grow and thrive to learn more about the HVAC industry throughout his career. Mas Broto is also a blogger, who's dedicated to bringing you the best knowledge to get ahead in the game of life.