Subaru LEGACY 2002 Quick Reference Index page 509

B: RHD MODEL
1. MECHANISM
The expansion valve accomplishes the function of atomizing the high-pressure liquid refrigerant
delivered from the modulator by a throttle valve with variable opening, thereby controlling the re-
frigerant for optimum heat exchange in the evaporator.
It consists of a needle valve (ball), temperature sensing tube, diaphragm, spring, etc. The upper
chamber of the diaphragm is filled with freon gas HFC134a.
The temperature sensing tube, provided at the outlet of the refrigerant that has passed through
the evaporator, senses the temperature of the gas refrigerant.
2. FUNCTION
The temperature of the refrigerant that has passed through the evaporator is sensed by the tem-
perature sensing tube, and the volume of freon gas in the diaphragm chamber changes to adjust
the opening of the needle valve.
! When the refrigerant temperature is low (when the heat load is small), the volume of freon gas
decreases, moving the temperature sensing tube to the left to reduce the opening of the needle
valve.
! When the refrigerant temperature is high (when the heat load is large), the volume of freon gas
increases, moving the temperature sensing tube to the right to increase the opening of the needle
valve.
EXPANSION VALVE
Low-pressure (To evaporator)
High-pressure (From modulator)
AC-37
HVAC System (Heater, Ventilator and A/C)
B4H0662B
B4H0663A