K 1500 Suburban 4WD V8-393 6.5L DSL Turbo VIN S (1996)
Expansion Block/Orifice Tube: Description and Operation
OPERATION
The orifice tube provides a restriction to the high-pressure liquid refrigerant in the liquid line, metering the flow of refrigerant to the evaporator as a
low-pressure liquid. The expansion tube and orifice are protected from contamination by filter screens on both inlet and outlet sides. The tube is
serviced only as a replacement assembly.
When the engine is turned "OFF" with the air conditioning operating, the refrigerant in the system will flow from the high-pressure side of the
expansion tube (orifice) to the low-pressure side until the pressure is equalized. This may be detected as a faint sound of liquid flowing (hissing) for 30
to 60 seconds and is a normal condition.
When system diagnostics indicate a restricted expansion tube, it may not be necessary to replace it. Metal chips, flakes, or slivers found on the screen
may be removed with compressed air. The expansion tube may be reused if:
^ The plastic frame is not broken.
^ The expansion tube is not damaged or plugged.
^ The screen material is not torn.
^ The screen is not plugged with fine gritty material.
