Front

The front "H" valve-type thermal expansion valve (TXV) is located at the dash panel between the liquid and suction lines, and the A/C evaporator. The assembly consists of an aluminum H-valve body and a thermal sensor. On vehicles equipped with the automatic temperature control (ATC) heater-A/C system, the evaporator temperature sensor is installed on the top of the expansion valve.

High-pressure, low temperature liquid refrigerant from the liquid line passes through the expansion valve orifice, converting it into a low-pressure, low-temperature mixture of liquid and gas before it enters the evaporator coil. A mechanical sensor in the expansion valve control head monitors the temperature and pressure of the refrigerant leaving the evaporator coil through the suction line, and adjusts the orifice size at the liquid line to let the proper amount of refrigerant into the evaporator coil to meet the vehicle cooling requirements. Controlling the refrigerant flow through the A/C evaporator ensures that none of the refrigerant leaving the evaporator is still in a liquid state, which could damage the compressor.

The A/C expansion valve is a factory calibrated unit and cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.