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HomeRepair HelpLennox A/C RepairLennox Air conditioner compressor won't run Repair
Lennox Air conditioner compressor won't run
If your Lennox air conditioner compressor won’t run, the unit may still blow air but never cool properly because the refrigeration cycle is not starting. The most likely cause is a failed temperature control thermostat, which can still power the fan motor while not sending power to the compressor. Next, check the temperature control board, since it supplies voltage to the fan motor and compressor, but confirm the compressor overload, capacitor, and compressor are good before replacing a board. A defective thermostat can also keep the AC compressor from turning on, followed by a burned-out overload that has lost continuity. The compressor itself may be bad, though this is less common and should be replaced only by a licensed technician. A faulty thermistor can also cause a compressor not starting condition if it cannot properly sense temperature. If your Lennox air conditioner compressor is not working, enter your model number on RepairClinic.com to find the exact thermostat, control board, overload, thermistor, or other replacement part made for your specific air conditioner.
01 - Lennox Air Conditioner Temperature Control Thermostat
The temperature control thermostat has electrical contacts inside that burn out over time. It is possible for the thermostat to still turn on the fan motor but not the compressor motor.
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Highly Likely
02 - Lennox Air Conditioner Temperature Control Board
The temperature control board provides voltage to the fan motor and compressor. If the control board is defective, it may stop providing voltage to the compressor. Control boards are often misdiagnosed. Before replacing the temperature control board, make sure you check more commonly defective parts—particularly the compressor overload, capacitor and the compressor itself. If you are certain that all of the other components are working properly, replace the temperature control board.
Highly Likely
03 - Lennox Air Conditioner Thermostat
The thermostat monitors the temperature of the air. When the air temperature rises above a set point, the thermostat activates a switch to provide power to the fan and compressor. If the thermostat is defective, it may prevent the compressor from running. If you determine that the compressor is at fault, replace it.
Highly Likely
04 - Lennox Air Conditioner Overload
The overload protects the compressor from burning out if it draws too much current. Over time, the overload can burn out. To determine if the overload is burned out, use a multimeter to test the overload for continuity. If the overload does not have continuity, replace it.
Highly Likely
05 - Lennox Air Conditioner Compressor
The compressor itself might be defective. However, this is not usually the case. Before replacing the compressor, be sure to check more commonly defective components—particularly the overload protector and the compressor capacitor. If the compressor is defective, it should only be replaced by a licensed technician.
Highly Likely
06 - Lennox Air Conditioner Thermistor
The thermistor is a sensor connected to the control board that detects the temperature of the outside air. If the thermistor does not have continuity, it can prevent the compressor from running. To determine if the thermistor is at fault, use a multimeter to test it for continuity. If the thermistor does not have continuity, replace it.
Common
Frequently Asked Questions
Why is my Lennox air conditioner fan running but the compressor won't run?
Can a bad thermostat cause my Lennox AC compressor not to start?
How do I test a Lennox air conditioner overload or thermistor when the compressor is not working?
Should I replace the control board if my Lennox air conditioner compressor won't run?
What if the compressor itself is bad on my Lennox air conditioner?
How do I find the right Lennox air conditioner replacement part?
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