AC Unit Running Outside But Not Inside

Posted by: Mas Broto

If your air conditioning (AC) unit is running outside but not inside, it can be frustrating and uncomfortable during hot weather. Here are some potential reasons why this may happen and some steps you can take to solve the issue.

Thermostat Issues

One of the most common reasons your AC unit is running outside but not inside is an issue with your thermostat. If your thermostat is not properly calibrated or is not communicating with the AC unit, it may not send the signal to the AC to turn on. In this case, you can try resetting the thermostat by turning it off, waiting for a few minutes, and then turning it back on.

If this doesn’t work, you may need to replace the thermostat or call a professional to diagnose and fix the issue.

Clogged Air Filters

Another common reason is due to clogged air filters. Air filters play an important role in removing dust, dirt, and other contaminants from the air before it enters the AC unit. If the air filters are clogged, they can restrict airflow and cause the AC unit to shut off.

In this case, you should replace the air filters or clean them if they are reusable.

Blown Fuses or Tripped Circuit Breakers

Your AC unit has two power sources: one from the inside of your home and one from the outside unit. If a fuse or circuit breaker has blown or tripped, it may only affect one power source, causing the AC unit to run outside but not inside.

Check your circuit breaker panel, reset any tripped circuit breakers, or replace any blown fuses. If the problem persists, you may need to contact an electrician to diagnose and fix the issue.

Blocked Condensate Drain Line

Another possible reason for your AC unit running outside but not inside is a blocked condensate drain line. Your AC unit removes moisture from the air as it cools, which is drained away through a condensate drain line. If this line becomes blocked, it can cause the AC unit to shut off.

You can try clearing the blockage by pouring a mixture of vinegar and water down the drain line or using a wet/dry vacuum to suck out the blockage.

Low Refrigerant Levels

Finally, if your AC unit runs outside but not inside, your refrigerant levels may be too low. Refrigerant is the substance that cools the air in your AC unit; if there is not enough of it, the unit may shut off.

If you suspect your refrigerant levels are low, you should contact a professional to inspect your unit and recharge the refrigerant if necessary.

What if ac unit runs inside but not outside?

Ok, if the AC inside is working and the outside is not, you can check a few things on your own.

The electrical power that feeds the outside unit has either a fuse or a disconnect switch. If the fuse blew, then you need to replace it. If there are no fuses on the outside, you need to check your breaker panel or fuse panel in the house that feeds the unit. See if the breaker has tripped or the fuse has blown. Reset if it did happen, and you should be fine. Change the fuse if it blows. In any case, a professional technician is all that is needed if you rule out the breaker or fuse.

There are several reasons your AC unit is running outside but not inside. By taking the steps outlined above, you can diagnose and fix the issue, ensure that your AC unit is working properly, and keep your home cool and comfortable. If you cannot solve the issue, it’s best to contact a professional HVAC technician to inspect your unit and diagnose and fix any problems.

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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.