Expansion Valve: Description and Operation

The expansion valve is located at the front of the heater-A/C housing between the liquid and suction lines and the evaporator coil. The expansion valve sprays the refrigerant into the evaporator.

The expansion valve is a factory calibrated unit and cannot be adjusted or repaired. If faulty or damaged, the expansion valve must be replaced.




When the A/C compressor is switched on the pressure in the evaporator decreases causing the diaphragm (1) to flex downward in an arch. The tappet (3) follows the motion of the diaphragm and presses the valve ball (4) away from its seat against the force of the spring (5). The refrigerant is sprayed into the evaporator through the open valve. Since the motion of the diaphragm (1) is dependent on the intake pressure as well as the temperature at the evaporator output, only the quantity of refrigerant which can be evaporated optimally is injected.