Expansion Valve: Description and Operation

Front A/C Expansion Valve

Description






• Typical A/C expansion valve shown.

The A/C expansion valve controls the amount of refrigerant entering the A/C evaporator and is of a thermostatic expansion valve design. The A/C expansion valve consists of an aluminum H-valve type body (1) with an integral thermal sensor (2) and is located at the dash panel between the A/C refrigerant lines and the A/C evaporator.

Operation

The A/C expansion valve controls the flow of high-pressure, low temperature liquid refrigerant entering the expansion valve and converts it into a low-pressure, low-temperature mixture of liquid and gas before it enters the A/C evaporator. To meet the vehicles A/C cooling requirements, a mechanical sensor is used in the A/C expansion valve to monitor the temperature and pressure of the refrigerant leaving the A/C evaporator and then adjust the inlet port orifice size to allow only the proper amount of refrigerant to enter the evaporator. 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 A/C compressor.

• Replacement of the seals is required anytime a refrigerant line or expansion valve is disconnected. Failure to replace the rubber and metal dual-plane seals may result in a refrigerant system leak.

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