Thermostatic Expansion Valve

WARNING: This page is about a different car, the 2004 Mercury Monterey and 2004 Ford Freestar. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: An in-line filter is installed in the auxiliary evaporator inlet line at the floorpan spring lock coupling connection. A restriction in this filter may cause misdiagnosis of a failed thermostatic expansion valve. This filter must be inspected before a new thermostatic expansion valve is installed. A thermostatic expansion valve automatically regulates the flow of refrigerant into the auxiliary 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 thermostatic expansion valve. This temperature variation regulates the refrigerant flow to the auxiliary evaporator core.

When the bulb senses a high temperature, the thermostatic expansion valve opens and floods refrigerant through the auxiliary evaporator core.
When the bulb senses a low temperature, the thermostatic expansion valve starts closing to shut off the refrigerant to the auxiliary evaporator core.