When you turn on your air conditioner, the last thing you expect is to be greeted by a torrent of warm air. After all, isn’t an AC system supposed to cool your home? Unfortunately, there are plenty of reasons for your AC system to suddenly blow warm or hot air.

We’ll go through all of the possible causes below, some of which you can diagnose and even fix on your own. For the more serious problems preventing your AC from working properly, you’ll have the experts at Comfort Systems on your side.

Thermostat Issues

If you feel warm air coming from your AC system, check the thermostat first. Chances are the thermostat is set to the “ON” position instead of “AUTO.” What does that mean for your AC system?

When set to “ON,” the blower fan will run constantly, but the AC system won’t provide any cool air. Setting the thermostat to “AUTO” ensures that the blower fan will only run when the AC system is ready to deliver cool air. Check if the thermostat is also set to “COOL” and make sure the temperature set point – which is the desired temperature you want – is set below the ambient temperature of your home.

If you’re still getting warm air from your AC system, don’t hesitate to check the thermostat itself. Faulty wiring, corroded terminals, and a weak battery are common issues for thermostats on the fritz.

Airflow Restrictions

In a nutshell, AC systems work by extracting unwanted heat from indoor spaces and releasing that heat to the outdoors. That means your AC unit needs good airflow to get the job done. Any type of reduction in airflow can put a damper on its performance, which in turn could cause it to blow warm air.

Make sure your air filter isn’t clogged with dust and debris. If it is, replace it immediately. Most technicians recommend replacing your air filters every 3 months or at the start of each season. If you or anyone else in your home has allergies, consider changing those filters on a monthly basis.

If possible, take a look at the evaporator coil (the part inside your AC unit that extracts indoor heat from inside your home) and make sure it’s not caked with dust and debris. Do the same for the condenser coil that’s in the outdoor portion of your AC unit. Make sure it’s not covered in leaves and other yard debris.

Both the evaporator and condenser coils are delicate components. You’re better off having our seasoned technicians take care of the cleaning. It’s also a good idea to have those coils checked twice a year for damage as well as debris.

Refrigerant Leaks

Not having enough refrigerant in your AC system can also cause it to blow warm air. Unlike other gases or liquids, the refrigerant inside your AC system won’t evaporate or dissipate as long as it remains properly sealed. When there’s a pinhole leak or a failed connection in one of the refrigerant lines, however, the resulting refrigerant loss can cripple your AC unit’s ability to cool your home.

Aside from the occasional hissing noise or a frozen coil, it’s hard to tell when there’s a refrigerant leak. Your best bet is to have one of our technicians check your AC system for leaks. Most technicians use UV dye to quickly track down the source of the leak.

Frozen Coils

Frost in your freezer is one thing, but seeing your AC unit encased in ice is an entirely unexpected sight. It all comes down to the way your AC unit operates. Warm air tends to hold more moisture than cool air and the process of extracting heat from indoor air causes that moisture to drop out as condensate.

If there’s no way for the condensate to drain away from the coils or if there’s not enough refrigerant in the system, frost can form on the coils. Heavy frost or ice build-up can bring your AC unit’s cooling duties to a halt.

If you’re dealing with a frozen coil, here’s an opportunity to put that warm air to good use. Shut off your AC system, but leave the blower fan running in the “ON” position for a few hours. Doing so will allow the frost to melt back into condensate. Make sure the condensate drain line is clear and intact to avoid any leaks or backups.

If you need a faster way to defrost your AC system, grab a hairdryer and set it on its highest setting. Carefully run the hairdryer over the frozen coil, making sure to not linger on one spot for too long.

Power Loss

With split air conditioners, you’ll need both indoor and outdoor units to run in sync to cool your home. If the indoor portion is powered up but the outdoor portion isn’t, then you won’t get anything but warm air from your AC system.

Check the “ON/OFF” switch near the outdoor unit and make sure it isn’t set to “OFF.” If everything checks out there, move on to the breaker panel inside your home and make sure the breaker for your AC system wasn’t tripped. If so, reset the breaker and watch carefully just in case the breaker trips again. If it does, then it’s time to have one of our technicians take a closer look at your AC system.

Posted in Air Conditioning