Thermostatic Expansion Valve

WARNING: This page is about a different car, the 2003 Ford Pickup, 2003 Ford F550 Super Duty, 2003 Ford F450 Super Duty, and 2003 Ford Excursion. However, it is still accessible from the selected car via links, so may be relevant.

An A/C evaporator expansion valve (19849) 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.