Expansion valve
The expansion valve regulates the amount of refrigerant that is released into the evaporator and is located in the engine compartment where the A/C piping enters through the bulkhead.
The expansion valve consists of a spring-loaded ball which is located on the high pressure side. The ball is connected via a pushrod to a diaphragm in a gas-filled chamber on the expansion valve low pressure side. The spring exerts constant pressure on the ball. The pushrod pressure on the ball depends on the pressure in the gas-filled chamber. The pressure in the gas- filled chamber depends in turn on the refrigerant temperature in the evaporator outlet.
When the temperature of the refrigerant from the evaporator that passes the expansion valve low-pressure side decreases, so does the pressure in the gas-filled chamber. The spring then presses against the ball and the pushrod, the diaphragm cannot resist the pressure and the flow area in the expansion valve decreases.
When the temperature of the refrigerant from the evaporator increases, so does the pressure in the gas-filled chamber. The diaphragm then presses against the pushrod and ball, the spring contracts and the expansion valve opens so that more refrigerant is allowed through, increasing the cooling efficiency and lowering the evaporator temperature.
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Gas-filled chamber
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