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HomeRepair HelpLennox A/C RepairLennox Air conditioner not cooling Repair
Lennox Air conditioner not cooling
If your Lennox air conditioner is not cooling, start with the airflow and control parts before assuming the sealed system has failed. A clogged air filter is the most likely cause, since restricted airflow can reduce cooling and cause the evaporator coil to frost over. Next, the user control and display board may keep the unit from setting or responding to the correct cooling temperature. Dirty condenser coils can also make the AC not cooling problem worse by preventing heat from leaving the refrigerant, which can make the compressor run continuously without cooling the room properly. If the fan motor or compressor will not run, a failed dual run capacitor is a common suspect. The compressor itself can fail, but check the overload, capacitor, and other more common parts first, since compressor replacement should be handled by a licensed technician. A faulty thermistor can also cause poor temperature sensing. Enter your Lennox model number on RepairClinic.com to find the exact air filter, control board, capacitor, thermistor, or other replacement part that fits your specific air conditioner.
01 - Lennox Air Conditioner Air Filter
If the air filter is clogged, air cannot flow properly through the air conditioner. This greatly reduces the cooling capacity of the air conditioner. In addition, if the air filter is clogged, the evaporator coils will frost over. Most air filters used in stand-alone air conditioners can be cleaned with soap and water. Only filters that are extremely clogged with debris or damaged will need to be replaced.
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02 - Lennox Air Conditioner User Control and Display Board
The user control and display board allows the user to operate the unit by selecting fan speeds and cooling temperatures. If the board is defective, it may not allow the unit to be set to a proper cooling temperature. If the temperature sensor or thermistor tests appropriately with a multimeter, it's possible the user control and display board is malfunctioning and will need to be replaced.
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03 - Condenser Coils are Dirty
The condenser coils dissipate the heat as the refrigerant passes through the coils. If the condenser coils are dirty, they won’t be able to dissipate the heat as effectively. As debris builds up on the coils, the air conditioner will become less efficient, causing the air conditioner to work harder to cool down. If the coils are significantly dirty, the air conditioner will not be able to maintain the proper temperature, and the compressor will run continuously in an attempt to cool the room. Check the condenser coils to determine if they are dirty. Refer to owner's manual for cleaning instructions.
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04 - Lennox Air Conditioner Dual Run Capacitor
A dual run capacitor will power both the compressor and the fan motor. If the capacitor burns out, the compressor or fan motor will not run. To determine whether the capacitor is burned out, use a multimeter to test it for continuity. If the capacitor does not have continuity, replace it.
Highly Likely
05 - Lennox Air Conditioner Compressor
The compressor 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 air. The resistance value of the thermistor changes in conjunction with the air temperature. If the air temperature rises, the resistance value will decrease. To determine if the thermistor is at fault, use a multimeter to test it for continuity. If the thermistor does not have continuity, or if the resistance of the thermistor does not change with a change in temperature, replace the thermistor. (To find specific temperature and resistance values, try checking your user’s manual.)
Common
Frequently Asked Questions
Why is my Lennox air conditioner not cooling?
Why is my Lennox AC blowing warm air even though it is running?
Can a dirty air filter cause my Lennox air conditioner coils to freeze?
How do I know if the thermistor is causing a Lennox air conditioner temperature control problem?
How do I find the right Lennox air conditioner replacement part?
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