Check These Items if Your AC Isn't Cooling

Fan blowing on woman

Why is your AC blowing warm air?

ESSEX August 22, 2019 —

Summer is in full swing and we all rely on the comfort of our homes to provide much needed respite from the heat. This is when we count on our air conditioners the most. If you’ve been asking yourself, “Why is my air conditioner blowing warm air?” here are some possible explanations:


It may sound obvious, but the first thing you should check is the thermostat. If your AC is blowing hot air, the thermostat may have been accidentally set to “heat.” If this is the case, it’s easy to fix on your own. Simply flip the thermostat setting back to “cool” and see if the air conditioner begins to blow cool air again.

The Fix: Check the thermostat and make sure it is set to “cool” and at the proper temperature. If it needs new batteries, replace them. During the cooling season, we recommend setting the thermostat to around 78 degrees Fahrenheit and 7-10 degrees higher while away from home.

Circuit Breaker

After checking the thermostat batteries and setting, make sure the HVAC system has power by checking the electrical panel. HVAC units require a lot of power to run. When there is too much power demand, the circuit breaker may shut off power automatically as a safety precaution.

The Fix: Locate your electrical panel and look for a tripped breaker or blown fuse. To turn power back on to the unit, flip the breaker completely off (opposite direction of all the other breakers), and then flip it to the “on” position. If you have a blown fuse, you will need to replace it. This may also be a good time to label all of your circuits for easy reference the next time there is an overloaded circuit.

Evaporator Coils and Air Filter

Although air filters have nothing to do with air temperature, a dirty air filter can lead to a dirty evaporator coil. When the evaporator coil gets clogged with dust and debris, there may not be enough free airflow to allow for proper cooling operation. You may think that frozen means cool air, but the frozen coils actually impede the flow of cool air, which can lead to warm air flow from the running motor instead.

Air filter replacements should be completed by the owner every 30-60 days, depending on the climate, filter type, and household. We recommend setting a monthly reminder to check the condition of your air filter at the start of every month.

The Fix: If your evaporator coil is frozen, turn the unit off and change the air filter. Wait until the unit has thawed before turning it back on again. If the coils freeze up again, you may have a refrigerant leak or a problem with the compressor. Turn the unit off and immediately call Contemporary Air Systems.

Condenser Coils (outdoor unit)

Just as the indoor evaporator coils need free airflow, so do the outdoor evaporator coils. That’s why we recommend you maintain a minimum 2-foot clearance around the outdoor condenser unit at all times.

The Fix: If your outdoor unit is clogged, turn off the unit at the source. Then, remove the larger items with gloved hands and rinse off the smaller debris with your garden hose.

Remember to schedule a professional air conditioning tune-up a at the start of every cooling season. In addition to professional cleanings, it’s a good idea to periodically check the outdoor unit and clean it yourself when necessary.


One of the main causes of a malfunctioning air conditioner is low refrigerant. If you have a worn service valve, loose joints, or poor assembly, you could have undercharged or overcharged refrigerant.

The Fix: Refrigerant (aka coolant) is highly dangerous. Never try fixing refrigerant problems yourself. The best way to prevent refrigerant leaks in the first place is to schedule annual air conditioning tune-ups before the cooling season begins. If you do notice your AC blowing warm air, hissing/gurgling noises, or ice on your refrigerant line, act quickly. The sooner you respond to under or overcharged refrigerant the better. Contact Contemporary Air Systems as soon as possible.

Additional Summer Air Conditioning Tips:

  • Keep your thermostat at 78° while at home and 7-10 degrees higher while away.
  • Use your ceiling fan to feel around 4° cooler.
  • Prevent moisture problems with proper ventilation.
  • Sign up for our Home Comfort Club so you never forget annual tune-up appointments.
  • Set reminders to check your air filter every 30 days.
  • Keep doors and windows closed when running the air conditioner.
  • Clean and dust your home regularly.
Contemporary Air Systems, Inc.
   613 Eastern Blvd.  •  Essex, MD 21221
   (410) 391-3070
   Monday - Friday:   8:30AM - 5:00PM
Saturday:   8:30AM - 12:00PM
Contemporary Air Systems, Inc.
   613 Eastern Blvd.  •  Essex, MD 21221
   (410) 391-3070
   Monday - Friday:   8:30AM - 5:00PM
Saturday:   8:30AM - 12:00PM
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