Rear A/C Expansion Valve

Rear A/C Expansion Valve:

The rear A/C expansion valve controls the amount of refrigerant entering the rear A/C evaporator. The rear A/C expansion valve is of an externally-equalized thermostatic expansion valve (TXV) design and consists of a cast metal body with a removable equalizer tube and an integral thermal sensor which uses a capillary tube and sensing bulb.

The rear A/C expansion valve is located to the left of the rear blower motors in the rear evaporator housing.

High-pressure, high 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 A/C evaporator. A thermal sensor in the rear A/C expansion valve monitors the temperature of the refrigerant leaving the rear evaporator by use of a sensing bulb positioned next to the evaporator outlet tube. The thermal sensor adjusts the orifice size at the evaporator inlet to allow the proper amount of refrigerant into the rear A/C evaporator in order to meet 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 cause damage to the A/C compressor.

To overcome the effect of the pressure drop within the rear A/C evaporator, an external equalizer tube is connected to the evaporator outlet tube and runs to the underside if the diaphragm within the expansion valve.

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