• The electronic control board continuously sends a flow of voltage, or signal current, through the thermistor.
The thermistor is sensitive to temperature fluctuations and changes resistance accordingly. When the
temperature rises in the refrigerator compartment:
• The thermistor resistance decreases, altering the signal going to the electronic control board.
• The electronic control board, sensing the change in the signal current:
a) Energizes the motorized air door to open.
b) Energizes the evaporator fan motor (if it is not already running during a compressor “on”
cycle).
When the refrigerator compartment temperature decreases:
• The thermistor resistance increases, altering the signal current to the electronic control board.
• The electronic control board sensing the change in the signal current:
a) Closes the air door.
b) Cycles the evaporator fan motor off (if the compressor is not running).
The electronic control board is operated by a variable resistor, or potentiometer, which sets the desired refrigerator
compartment temperature. Adjusting the potentiometer changes the sensitivity of the electronic control board to the
signal current from the thermistor. Varying the sensitivity raises or lowers the regulated temperature.
The refrigerator thermistor and the electronic control board directly affect the operation of the evaporator fan motor
and the motorized air door. Evaporator fan motor and motorized air door cycling may occur one or more times
before the freezer calls for a cooling cycle.
Control Interaction
The following information explains how the freezer thermostat and the refrigerator electronic temperature control
system interact.
When the freezer thermostat closes (calling for cooling):
• The cycle is initiated.
• A voltage signal is sent to the electronic control board.
• The electronic control board energizes the evaporator fan motor.
• If the thermistor is satisfied, the motorized air door remains closed.
• If the thermistor is calling for cooling, the motorized air door opens.
When the freezer thermostat opens (is satisfied):
• The cooling cycle is terminated.
• The voltage signal to the electronic control board is terminated.
• If the thermistor is satisfied, the motorized air door is closed and the evaporator fon motor is turned off.
• If the thermistor is calling for cooling, the motorized air door opens and the evaporator fan motor runs.
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