How to Troubleshoot an A/C Not Blowing Cold Air

Nobody wants to turn on the air conditioner only to find out that the vents aren’t blowing cold air. Well, it could be worse—at least it’s running.

While you may need a qualified technician to replace a part, such as a thermocouple, there are a couple of things you can try first to avoid a service visit from your local HVAC tech.

If your air conditioning isn’t cold or not cooling enough, continue reading. These simple fixes might fix your cold air problem.

What to Do If the Air Coming Out of Supply Vents Is Not Cold

If your AC is blowing warm or room-temperature air, try these troubleshooting tips first:

  1. Check the Thermostat

The first thing you should do is check your thermostat to make sure it is set to “cool” and the temperature setting is below your room temperature. Somebody may have purposefully or accidentally adjusted the thermostat without you knowing. Also, if you installed your thermostat recently, it may have been improperly installed. In this case, it would be best to contact a professional to make sure all of the wiring and terminals have been properly hooked up.

  1. Check the Air Filter

After checking the thermostat for proper operation, the next thing you should look for is a dirty air filter. Locate the filter door in your indoor air handler and remove the air filter. If your filter is really dirty and clogged, it could be impeding the airflow necessary for your air conditioning system to work.

Although a dirty air filter has nothing to do with how cold your conditioned air is, sometimes it can become so clogged as to cause frozen evaporator coils. When your evaporator coils freeze, it can cause a problem with the cooling process. If your evaporator coils are indeed frozen, replace the dirty air filter with a clean one and turn off the air conditioning system until the evaporator coils thaw.

  1. Check the Evaporator

Your evaporator coils are located in your indoor air handler, above the air filter. If you notice ice on your evaporator coils, make sure you have a clean air filter and turn off the unit until the ice has had time to thaw. If the coils continue to freeze, turn off the unit and wait for a professional technician to make the necessary repairs.

  1. Check the Condenser (Outdoor Unit)

Your condenser coils are located in the outdoor unit. They help transfer the heat that has been absorbed from inside your home to the outside air. Similar to your evaporator coils inside, the condenser coils need proper airflow in order to operate properly.

Take a walk outside and inspect your outdoor unit. Is there a lot of dirt, leaves, and other debris blocking the flow of air? Have your plants and bushes grown too close to the unit? In order for your outdoor unit to effectively transmit your indoor heat outdoors, it must have a minimum 2-foot clearance around the entire unit. If there is anything blocking the flow of air over your condenser coils, trim back the plants and remove any large debris by hand.

Once you are done removing the large pieces by hand, you can use your garden hose to get rid of the smaller pieces. Before you do this, however, make sure power to the unit has been turned off at the source (meaning your breaker box or the outdoor switch near the unit). Dirty condenser units are one important reason why it’s important to shedule regular air conditioning maintenance every year.

  1. Check the Power Switches

Make sure the service switches for your air conditioning unit are on. This means checking:

  • The breaker or fuse box. Look for any tripped or blown fuses. If any of the switches are set to the “off” position or somewhere in between “on” and “off,” you will need to flip the breaker completely off and then flip it back on again. Learn how to safely reset breakers and replace fuses here.
  • The switch near your indoor air handler (it is normally where your furnace is located).
  • The switch near your outdoor air conditioning unit (it is normally located on an exterior wall near your outdoor unit).

If any of these switches are turned off, it could affect the performance of your air conditioner. Make sure all the switches are in the “on” position. If you need help finding any of your HVAC switches, contact OnTime Service.

If none of the above tips have solved your problem, you may have a problem with your thermocouple, capacitor, or refrigerant. These repairs will require the expertise of a qualified heating and air conditioning technician.

If your air conditioner isn’t cooling your home properly and you live in the Birmingham, AL area, contact OnTime Service.


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Give OnTime Service a call to schedule your electrical safety inspections at 205-942-1405.

Our experienced team of electricians is fully trained to handle any electrical system.

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