F 150 4WD Pickup V8-281 4.6L VIN W EFI (1997)
Expansion Block/Orifice Tube: Description and Operation
NOTE: The A/C evaporator core orifice is replaced as an assembly and should also be replaced whenever the A/C compressor is replaced.
The A/C evaporator core orifice, located in the condenser to evaporator tube, is the restriction in the refrigerant system that creates the pressure drop
necessary for cooling by metering the flow of liquid refrigerant into the A/C evaporator core. The inlet filter screen acts as a strainer for the liquid
refrigerant flowing through the A/C evaporator core orifice. O-rings prevent the high-pressure liquid refrigerant from bypassing the A/C evaporator core
orifice.
