Expansion Valve: Description and Operation

Auxiliary Climate Control

An A/C evaporator expansion valve automatically regulates the flow of refrigerant into the auxiliary A/C evaporator core. It is also the dividing point in the system between low- and high-pressure sides.

The temperature sensing bulb measures the temperature of the refrigerant in the suction line and transmits it to the A/C evaporator expansion valve. This temperature variation regulates the refrigerant flow to the auxiliary A/C evaporator core.
^ When the bulb senses a high temperature, the A/C evaporator expansion valve opens and floods refrigerant through the auxiliary A/C evaporator core.
^ When the bulb senses a low temperature, the A/C evaporator expansion valve starts closing to shut off the refrigerant to the auxiliary A/C evaporator core.