How to Fix AC That's Not Cooling – Air Conditioner Repair
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How to Fix an Air Conditioner That's Not Blowing Cold air

About this repair:

  • Rated as REALLY EASY
  • 42 repair stories

Air Filter

Your window air conditioner may not be able to blow cold air if the air filter is clogged, restricting air flow. Air conditioners use a fan to circulate cold air over the evaporator coils and into your room; a clogged air filter impedes that air flow. If the air filter is dirty, the restricted air flow can cause a buildup of frost or ice on the coils, which can lead to other problems. You can usually locate the air filter behind the front grille. Clean the filter, or replace it if it is too dirty or damaged to function. Take this opportunity to also clean the fan blades and evaporator coils with soap, water, and a soft brush.

Fan and Fan Motor

The reason your air conditioner is not cooling could be because of an issue with the fan or fan motor. In window air conditioner units, the fan helps circulate cool air over the evaporator coils and throughout your room. If the fan fails or is running slowly, the air won’t flow properly, leading to a buildup of frost or ice on the coils. To access the fan and fan motor, remove the cabinet. Try turning the fan motor to see if it moves easily and freely. If the fan blades appear damaged, they will need to be replaced. If there is no apparent damage to the fan or fan motor, then live-voltage tests will need to be performed by a qualified technician.

Temperature Control

If your air conditioner won’t blow cold air, it could mean there is a problem with the temperature control or thermostat. This part monitors the room air temperature and signals the compressor to kick in if necessary. The temperature control often has a sensor bulb attached to it that will be located near the evaporator coils as well as electrical contacts for the compressor. The thermostat also signals the compressor to turn off when the ideal temperature is achieved. If the temperature control or thermostat has failed, it will not signal the compressor to cool the air properly. Check the sensor bulb for damage or kinks, and replace the control assembly if it is broken. If it has no outward signs of damage, rotate the dial to the lowest setting and test its continuity with a multi-meter. Be sure to check that the sensor bulb is positioned correctly before replacing the control.

Electronic Control Board or PCB Assembly

Your air conditioner may not blow cold air because of an issue with the control board, also sometimes known as a PCB assembly. The control board works with the temperature sensor to signal the compressor to turn on according to the desired room temperature. If the control board is not working, it won’t power the compressor to turn on and begin cooling air. First check the thermistor/temperature sensor for damage before concluding that the control board needs to be replaced.


If your window air conditioner is not cooling, it could be due to an issue with the compressor circuit, specifically the capacitor. This part aids the compressor to start and blow cool air into the room. If the capacitor isn’t working, the compressor will not start. To access the capacitor, remove the cabinet cover and inspect it for damage. If the capacitor isn’t obviously damaged, a live-voltage test will need to be performed by a qualified technician. It is essential that the replacement capacitor conforms to the same specifications as the previous one.


If your window air conditioner will not blow cold air, and you have already ruled out the air filter and fan motor for issues, the problem may be the thermistor. This part helps to control the temperature and signal the compressor to power on and begin cooling if necessary. The thermistor is typically located next to the evaporator coil. Locate the thermistor and check for signs of damage, replace it if necessary.

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