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Why Is My AC Blowing Warm Air?


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Summers in California create unique challenges for keeping Fremont homes comfortable. One of the most common issues is arriving home to an air conditioner that’s blowing warm air. But when this happens to you, there’s good news: It might be a quick fix.

We’ve assembled this guide so that you can quickly determine if DIY troubleshooting will fix the issue or if you’ll need to schedule AC repairs.


The Evaporator Coils Are Dirty

In a functioning AC, warm air blows over the evaporator coils, cooling the air to the temperature you’ve designated on your thermostat. Over time, the evaporator coils gather a film of dirt.

DIY or Professional Service? You can clean the coils yourself, or you can call the professionals. Many homeowners never have to worry about cleaning the coils because they schedule routine AC maintenance, and this task is automatically completed by a professional once or twice a year.

If you want to do this as a DIY project, you’ll need to turn off the unit at both the breaker panel and the wall, remove the cover on the outdoor unit, then wipe the coils clean with soapy water and a cloth.

A Circuit Breaker Tripped

Some homes are wired with separate indoor and outdoor circuit breakers, placing the fans in the outdoor AC unit on a separate breaker from indoor components.

DIY or Professional Service? You can solve this issue yourself by heading to your circuit breaker panel. Ensure all breakers are switched to “on,” and your outdoor unit should have power again. You’ll need to schedule AC repairs if tripped circuit breakers happen frequently.

Your Thermostat Needs a Reset

Thermostats are the brain of your HVAC system. They can be tricky to operate, especially if different household members constantly adjust the settings and temperature.

DIY or Professional Service? Try to DIY this issue before calling a pro to recalibrate your thermostat. In most cases, “auto” is the setting you want. If you’re still not as comfortable, switch to the “cool” setting. The “fan” setting just blows unconditioned air through your vents which isn’t ideal in the summer.

Refrigerant Has Leaked

In an AC unit, refrigerant fills the evaporator coils and cools the air that passes through them. If there’s a leak in the refrigerant line leading to the coils, the AC will blow warm air into your home.

DIY or Professional Service? You’ll need to call AC repair professionals to fix the leak and refill the refrigerant.

If you’ve enrolled in a routine HVAC maintenance program, a technician will regularly check for signs of a refrigerant leak. You’ll know that you have a refrigerant leak if you see the coils are frozen, but the unit still blows warm air.

The Compressor Has Failed

As cool air leaves the evaporator coils, it becomes a low-pressure gas. The AC unit’s compressor takes the gas and compresses it to create blasts of cool air that keep indoor spaces comfortable in the summer.

If the compressor fails, you’ll notice growling or screeching noises and a slow start each time your system kicks on.

DIY or Professional Service? You’ll need to call a certified AC technician to repair or replace your AC compressor.


Schedule AC Repairs With Local Experts

If you’re looking for trustworthy technicians to repair the air conditioner in your Fremont or Livermore home, call AIS Heating & Air Conditioning.

Our certified technicians will diagnose the issue quickly and provide quality AC repairs that restore your home’s comfort as soon as possible.

Request AC repairs today. Call (510) 792-4328 or contact us online.

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