Window Air Conditioner:
Evaporator fins are iced up
The evaporator fins ice up if the compressor runs constantly for one of these reasons: a dirty air filter restricts air flow; the air conditioner is too small for the room; the temperature setting is too cold; a control is defective. See the repairs below to help correct a problem with evaporator finds that ice up.
Replace the window air conditioner control thermostat
Some window air conditioners have an electro-mechanical thermostat instead of an electronic control board to control the on/off cycling of the compressor and fans. Replace the thermostat if it fails to control the compressor and fans properly.
Replace the window air conditioner evaporator thermistor
The evaporator thermistor is a temperature sensor that is mounted on the evaporator. It monitors the temperature of the evaporator to detect excessive frost on the evaporator.
The thermistor communicates that temperature to the electronic control board through a wire harness connection.
If the evaporator frosts up, the electronic control board will detect the frost according to the temperature communicated through the thermistor.
If the thermistor is defective, the electronic control will not properly detect and eliminate the frost.
Replace the evaporator thermistor if it doesn't properly detect the evaporator temperature.
How to replace a window air conditioner electronic control board
When a window air conditioner won't cool or won't start at all, the electronic control board might be the problem.
This step-by-step repair guide shows how to replace a window air conditioner electronic control board.
45 Minutes or less
How to replace a window air conditioner ambient thermistor
If your window air conditioner isn't cooling the room very well, the ambient thermistor might be at fault.
This DIY repair guide explains how to replace a window air conditioner ambient thermistor with step-by-step instructions.