Cause 1

Main Control Board

The main control board has an infrared receiver that receives signals from the remote. If the infrared receiver is not working, the remote control will not be able to communicate with the control board. If you suspect the main control board is defective, replace it.

Cause 2

Remote Control

First, try replacing the batteries in the remote control. If installing fresh batteries doesn’t solve the problem and you can still operate the air conditioner manually, the remote control might be defective. If you think the remote control is defective, replace it.

Cause 1

Relay Board

The relay board provides voltage to many components of the air conditioner, including the fan motor. If the relay board isn’t working properly, the fan might not run. Relay boards are often misdiagnosed; before replacing the board, make sure you check more commonly defective parts—particularly the fan motor capacitor and the fan motor itself. If you are certain that all of the other components are working properly, replace the relay board.

Cause 2

Fan Motor

Try turning the blade by hand. If the blade does not turn freely, this indicates that the motor bearings are worn out. If the motor bearings are worn out, replace the motor. If the blade turns freely, test the incoming power to the fan motor. If power is getting to the fan motor, but the motor won’t run, this also indicates that the motor is defective and should be replaced.

Cause 3

Dual Shaft Fan Motor

The dual shaft fan motor (or circulation fan motor) might be defective. The circulation fan motor has two fan blades: one on either side of the motor. On one side, the fan blade draws in outside air over the condensing coil to dissipate the heat. On the other side, the fan blade directs the air over the evaporator coil. The dual shaft fan motor has bearings that can loosen or bind over time. To determine if the motor bearings are defective, wiggle the motor shaft. If the motor shaft is loose, or if it won’t turn at all, replace the fan motor.

Cause 1

Sealed System Leak

If the air conditioner coils are freezing in only one area, there may be a sealed system (or refrigerant) leak. This is normally a very expensive repair. Repairs to the sealed system must only be performed by a licensed technician.

Cause 2

Dirty Air Filter

If the air filter becomes clogged with dirt, it restricts airflow over the evaporator coils. If the airflow is reduced, the evaporator coils get too cold, which then causes the humidity in the room to condense on the coils and freeze. As frost accumulates on the coils, the frost restricts the airflow even more. Eventually, the entire evaporator coil assembly will frost over, causing the airflow to be completely restricted. If the air filter is dirty, replace it.

Cause 1

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.

Cause 2

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. If the condenser coils are dirty, clean them.

Cause 3

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. To remove debris from the air filter, try cleaning the filter. If it is not possible to clean the air filter, replace it.

Cause 1

Leaning Too Far Forward

If the window or through-wall air conditioner is leaking water from the front, this indicates that the air conditioner is leaning too far forward. The air conditioner is designed to expel the condensate water from the back of the unit. Because of this, the air conditioner must be installed so that it leans back on a 1-2 degree angle.

Cause 1

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.

Cause 2

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.

Cause 3

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.

Cause 1

Fan Blade

Air conditioners have a fan blade in the front and a fan blade in the rear. Check both fan blades for damage. If a fan blade is damaged, or is rubbing against the fan housing, replace it.

Cause 2

Dual Shaft Fan Motor

The fan motor or dual shaft fan motor has bearings which are usually permanently lubricated. However, over several years, the lubrication will break down, causing the motor to become noisy. If this happens, replace the dual shaft fan motor.

Cause 3

Compressor

When the compressor is wearing out, it generates more noise than usual. When this happens, it is not necessary to replace the compressor—compressors often last for years after they become noisy. However, if you would prefer to have a new compressor, have a licensed professional replace it.

Cause 1

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 cause the compressor to run continuously. To determine if the thermostat is defective, set the air conditioner to cooling and then use a multimeter to test the thermostat for continuity. If the thermostat does not have continuity while the air conditioner is set to cooling, replace the thermostat. (Note: Some thermostats may also control a heater and, as a result, will have three terminals. Refer to your air conditioner’s wiring diagram for more information.)

Cause 2

Temperature Control Thermostat

The temperature control thermostat provides voltage to the fan motor and compressor. If the thermostat has shorted out, it might send continuous voltage to the compressor and cause the compressor to run all the time. To determine if the thermostat is shorted out, use a multimeter to test it for continuity. If the thermostat has continuity all the time, this indicates that it is shorted out and should be replaced. (Note: Some thermostats may also control a heater and, as a result, will have three terminals. Refer to your air conditioner’s wiring diagram for more information.)

Cause 3

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. If the condenser coils are dirty, clean them.