K Yukon/Denali 4WD V8-5.7L VIN R (2000)
Expansion Block/Orifice Tube: Description and Operation
Expansion (Orifice) Tube - Front A/C System
The plastic expansion tube, with the mesh screen and orifice is in the condenser outlet pipe in all the models, except the models with rear air conditioning
(RPO C69). Models equipped with rear air conditioning use a Y-shaped junction block in the tube between the condenser and the front evaporator. The
junction block is near the right side of the radiator support. The expansion tube (2) is between the junction block and the front evaporator.
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 filter screens on both the inlet and outlet sides protect the expansion tube and orifice from contamination. Service the tube only
as a replacement assembly.
When the engine is turned OFF with the air conditioning operating, the refrigerant in the system flows from the high-pressure side of the expansion tube
orifice to the low-pressure side until the pressure moves towards equalization. This is detectable as a faint hissing sound for 30-60 seconds. The hissing
is normal
When system diagnostics indicate a restricted expansion tube, replacement of the restricted expansion tube may not be necessary. Metal chips, flakes, or
slivers found on the screen may be removed with compressed air. Reuse the expansion tube under the following conditions:
-
The plastic frame is not broken.
-
The expansion tube is not damaged or plugged.
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The screen material is not torn.
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The screen is not plugged with fine gritty material.
For a description of the RPO Code(s) shown in this article/image, refer to the RPO Code List found at Vehicle/Application ID.
See: Application and ID
