Thermostatic Expansion Valve

WARNING: This page is about a different car, the 2004 Ford Pickup, 2004 Ford F550 Super Duty, 2004 Ford F450 Super Duty, 2004 Ford Excursion, and 2004 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

An thermostatic expansion valve (TXV) 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 TXV. This temperature variation regulates the refrigerant flow to the auxiliary A/C evaporator core.

When the bulb senses a high temperature, the TXV opens and floods refrigerant through the auxiliary A/C evaporator core.
When the bulb senses a low temperature, the TXV starts closing to shut off the refrigerant to the auxiliary A/C evaporator core.