Expansion Valve: Description and Operation

TXV Cross Section:

The Thermal Expansion Valve (TXV), with its monitoring bulb and attaching capillary, mesh screen, and variable orifice is located in the evaporator inlet pipe. While sensing the temperature of the evaporator outlet pipe, the monitoring bulb's internal pressure raises or lowers in direct proportion. (By sensing a higher temperature, the TXV opens further to allow more R-134a into the evaporator, and the opposite when it senses cooler temperatures). This provides a variable restriction for the high-pressure liquid refrigerant in the liquid line, which meters the flow of refrigerant to the evaporator as a low-pressure liquid. The thermal expansion valve is protected from contamination by a filter screen.

Do not attempt to change flow rate of the valve. It is preset for maximum performance. Any attempt to alter will reduce cooling capabilities and could possibly cause system damage.

The thermal expansion valve is located near the evaporator at the front of dash. The thermal expansion valve is serviced only as a replacement assembly.