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Window Air Conditioner Troubleshooting, A Step By Step Guide

With this window air conditioner troubleshooting guide, you get the technical knowledge to diagnose and repair your unit. The typical service call would cost over $100. With this guide, you can do it yourself and save that money.


You should begin your window air conditioner troubleshooting by ensuring that the routine maintenance has been performed on the unit.

Then, your window air conditioner troubleshooting should start with checking the different modes of operation to see which components operate. Turn the unit fan to on and the cool and heat modes off. If the fan does not operate, check the power supply to the unit. Check to see if the breaker or fuse for the unit is tripped. If the breaker/fuse is tripped, check to make sure that it is the proper size circuit for the unit you have. On some units, there is a current interruptor on the power cord to the unit. Check to see if it is tripped by pushing the reset button.

If the circuit is the proper size, then you can go ahead and reset the breaker/fuse. If it trips again, then you require further troubleshooting. Shut the power off and check all of the wiring in the unit to make sure that none of the connections is loose or damaged.

If the fan does not operate but the fuse/breaker is not tripped, you should check the run capacitors for the fan and compressor. If the capacitors are good but the fan motor does not operate, you can check the fan switch and the fan motor. Ensure that the fan blades spin freely.

If the fan motor operates but the compressor does not start, you should feel the compressor with your hand. If it is very hot, then you should allow it to cool. Then, you can take resistance measurements to make sure the compressor motor is good.

Then, you should attempt to start the unit in the cooling mode. As you do so, listen for a clicking sound which is an indication that it is attempting to start. If the compressor starts but does not cool properly, the unit may be low on refrigerant.

Window Air Conditioner Troubleshooting, Repair or Replace?

If the compressor attempts to start but shuts off very quickly, the compressor could be bad. Generally, if the compressor is bad on a window air conditioner, it is cheaper to replace the entire unit than to fix it.

You can check out our brand ratings to help you to choose the right brand to replace your broken unit.

If the compressor does not attempt to start, ensure that the thermostat is set below room temperature. On units with a mechanical control, you will hear a click when you adjust the temperature.

That is an indication that the thermostat is working properly. On units with an electronic control, you can take a resistance reading of the temperature sensor to verify it is good. If the sensor is good and the compressor checks are ok, then the control board is probably bad.

You should complete your window air conditioner troubleshooting by observing the unit's operation through a complete cooling cycle. During this time you should check the difference between the temperature of the air entering the unit and the temperature of the air leaving the unit. There should typically be a ten to fifteen degree difference.

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