Why is the Air Conditioner Window Unit Not Blowing Cold Air?

By Roz Zurko

If you turn your air conditioner on high and cold air does not blow out, you know you have a problem. There is no need to panic, however, as you watch the thermometer rise. You may be able to fix the unit yourself by doing a quick check and making a few minor adjustments. You can have that cold air blowing out of your unit again in a matter of minutes with a few simple troubleshooting tips.

Air conditioner in window
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Box air conditioner in a window.


Ventilation panel in residence
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Ventilation inside a home.

It may just be the extreme heat and humidity causing the perception that the air is not cool. If it is the first extremely hot or humid day in the cooling season, it may take longer than usual for the air provided by your air conditioner to cool off your room or home. Give it longer than usual to get the air cooled. If your unit is baking in the hot sun, this can also cause it to take a longer period of time to get the air cooled. Give the unit at least 20 minutes and come back and check again. If the unit is in a window and cools off one room, close the door and come back to see if the temperature has gone down.

Quick Fixes

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Check the thermostat on your unit and make sure it is lower than the actual temperature in your house. To test this, put your thermostat about 10 degrees lower than the house temperature and see if the condenser kicks on and starts cooling off the air. For a programmable thermostat, make sure the batteries are not dead.

Clean your air filter. If the filter is clogging the air flow due to build up, then your unit is overworking. This will cause the air not to be as cool as the unit is capable of providing. Providing your air conditioning unit with a clean air filter will let it work to its capacity and you will get cool air.

Frozen Unit

Woman drinking coffee
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Woman sitting near cool blowing air from air conditioner.

Open the unit and check to see if ice has formed inside. Cool air will not be provided if your unit has frozen up. This happens when the unit is on for long periods of time during extreme hot and humid weather. Turn the unit off and leave it uncovered to defrost. You can help the defrosting process by using a hair blower, set on "Low," to melt the ice. Once the unit is defrosted, put the cover back on and try it again. The air should be cool. Guard against this happening again by turning the unit off periodically for an hour or so. The best time to turn the unit off is while you are sleeping during the night. The cool air will stay in the house until morning and you will not be overworking your air conditioning unit.