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Air Conditioner Not Cooling

  • Others
  • Others
  • Troubleshooting
  • Air Conditioning Units
  • Last Updated 22/07/2014


There are several factors that may affect the cooling performance of your air conditioner. Proper installation, operation, and maintenance are all necessary to ensure that the air conditioner is operating at peak performance. It is important to make the distinction of when and how long you have been experiencing the issue, and how long the air conditioner has been installed.

New Unit, Just Installed

It is important that if your air conditioner is a new unit that it is sized appropriately for the space that it is attempting to cool. If the air conditioner is too small, it will run constantly but not be able to cool the space. If the unit is too large, it will short cycle (turn on and off continuously) cooling the immediate area around the unit, but not the rest of the room. If the air conditioner is not sized appropriately, it is advised that the unit be swapped for the correct size.

Your air conditioner must also be on a dedicated circuit breaker. If other devices are drawing power from the same breaker, there is not enough for the air conditioner to operate completely. The fan may run but the compressor will not be able to turn on to cool. Remove all other devices from the outlets that draw from the same circuit breaker as the air conditioner, or have an electrician install a dedicated circuit breaker for the air conditioner.

It is also important to check the mode that your air conditioner is set to. In order for your air conditioner to cool, it must be set to either COOL or ENERGY SAVER mode. If the air conditioner is in fan mode, the compressor will not turn on to cool. Put the unit in cool mode and let it run for a few hours. Monitor the room for temperature changes.

The temperature on your air conditioner should also be set at least 5°F lower than the room temperature; otherwise the compressor may not turn on to cool the space.

It is also important that the unit be installed properly.

Just Reinstalled Last Year’s Unit

If you used your air conditioner last year and it worked fine, there are a few steps you may need to perform in order for the unit to operate efficiently.

It is recommended that the air filter, evaporator coils, and condenser coils are cleaned prior operating the unit for the first time of the season. Dust from last year, or even being stored over the winter, may restrict the air flow and prevent proper cooling.

If the air conditioner was installed in the same location, using the same plug as last season, make sure there has been no change to the outlet or the power supply from the breaker. Plug another device into the outlet and check the breaker to make sure it has not tripped.

Unit Has Been Working Fine

The air filter on your air conditioner should be cleaned at least every two weeks. The evaporator and condenser coils should be cleaned as needed.

The hotter the temperature is outside, the less heat that is discharged out of the back of the unit. This results in slower cooling during the hottest parts of the day. It may be necessary to lower the set temperature so the unit will run more. Another option is to install an awning over the air conditioner to shade it from the sun.

If the temperature outside is below approximately 95°F, make sure the temperature is set far enough below the temperature in the room to cool effectively. Closing the blinds and curtains will block the sun and excess heat from entering the room and insulate the cooler air better.

If you have a window unit, remove the front grille and see if there is any frost buildup.

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