Impreza 25 RS Coupe F4-25L SOHC (2000) Expansion Valve Mechanism
Expansion Valve: Description and Operation
Function
Expansion Valve
If the heat load of the air conditioner system increases, the refrigerant temperature at the evaporator outlet rises and therefore increases the pressure P(1)
at around the temperature sensing area. As this pressure P(1) becomes higher than the resultant force of evaporator outlet (low pressure side) pressure
P(2) and the spring force F (P(1) > P(2) + F), the diaphragm is pressed down, opening the valve ball connected to the diaphragm to increase the flow of
the refrigerant.
If the heat load decreases, the action contrary to the one mentioned above takes place, closing the valve to decrease the flow of the refrigerant.