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Why Is My Air Conditioner Blowing Warm Air?

Reasons Why Your AC System Might Not Be Working Right

When summer is at its peak, that’s when you rely on your air conditioner the most. So, it would be a huge disappointment to find your unit blowing warm air instead of providing you much-needed relief from the heat. This problem is common in HVAC systems. In some cases, you might even be able to fix it on your own.


Here are some tips on troubleshooting an air con unit that blows hot air, and how to fix them:


When you notice your AC blowing hot air, the first thing to check should be the thermostat. It might have been set to “heat” by accident, and this is easy to fix. Just switch the thermostat back to “cool”, then check if the unit starts to blow cool air.

You should also check that the batteries are functioning, and the temperature isn’t set too high.

Circuit Breaker

Once you’re done checking the thermostat settings and batteries, make sure that the unit has power. Do this by inspecting the electrical panel. An AC unit needs a significant amount of power to function. When there is excessive power demand, your circuit breaker may automatically shut off as a safety measure.

To fix the problem, find the electrical panel. Look for a blown fuse or tripped breaker. Flip the breaker off completely, then switch it on to power the AC. In case of a blown fuse, replace it. Contact an HVAC pro like Spartan Plumbing if the breaker still trips from time to time for no apparent reason.

Air Filter and Evaporator Coils

While air filters don’t directly affect air temperature, they can lead to evaporator coil problems when dirty. It may get clogged with debris and dust that can hamper proper cooling operation. Your evaporator coils may freeze. You may think that this may mean cooler air, but, in reality, this can cause hot air to flow from the motor.

To prevent the problem, replace your air filters every 30 to 60 days, depending on the filter type, household, and climate. To be sure, inspect your air filters each month. Hold them up to the light. If the light barely passes through, it is time to replace the filters.

If the evaporator coil is frozen, switch the unit off, then change the filter. Don’t turn the unit back on until the unit has thawed. If the coils start to freeze again, switch the AC off right away, then call a technician to properly troubleshoot the problem, which may be a refrigerant leak or a compressor issue.

Outdoor Unit Condenser Coils

Your next step is to check the outdoor unit. The outdoor evaporator coils need to have unimpeded airflow, just like the indoor coils. Thus, you should always maintain at least 2-ft of clearance around your outdoor condenser unit.

If the outdoor unit is blocked, switch the AC off at the source. Remove the bigger items blocking the unit by hand, and rinse the smaller debris with a garden hose.

Before the start of every summer, schedule an AC cleaning and tune-up with a pro. Make sure to include complete outdoor and indoor coil cleaning.

Refrigerant or Coolant

A low refrigerant level can be the main cause of air conditioning malfunction. Over or undercharged refrigerant may be due to a worn out service valve, poor assembly, or loose joints.

Unless you are a certified technician, never attempt to fix refrigerant problems on your own. A regular tune-up scheduled at the start of every cooling season is the best way to prevent refrigerant leaks.

As soon as you notice your unit blowing hot air, freezing on the refrigerant line, or making gurgling/hissing noise, you should call an HVAC specialist right away.