Tahoe 4WD V8-393 6.5L DSL Turbo VIN S (1995)
Refrigerant Filter: Customer Interest
A/C Compressor - Loud Knocking Noise
File in Section: 1 - HVAC
Bulletin No.: 56-12-01
Date: February, 1995
SUBJECT:
Loud Knock from A/C Compressor (Replace Compressor and Thermal Expansion Valve)
MODELS:
1994-95 Chevrolet C/K Models built before VIN breakpoint SJ300349
1994-95 GMC Truck C/K Models built before VIN breakpoint SJ701253
with Rear A/C (RPO C69) or Rear Heater and A/C (RPOs C36, C69)
CONDITION
Some owner's of the above listed vehicles may comment that the A/C compressor has developed a loud knocking noise. The A/C system will continue to
cool.
CAUSE
When the rear A/C system is shut off, a refrigerant flood back condition may occur through the rear A/C system. This flooding degreases the internal
parts of the compressor resulting in rapid slider block wear and the resulting loud knocking noise. A poor contact between the TXV capillary tube and
the rear evaporator outlet tube can allow the TXV to remain open when the rear system is not in use. The open TXV may allow liquid refrigerant to flood
back through the rear system (liquid line, TXV, evaporator, rear suction line) and subsequently flood the compressor.
CORRECTION
Replace the A/C compressor, the thermal expansion valve (TXV), and add an in-line filter.
Service Procedure
1. Recover the R-134a refrigerant charge (Section 1-B of Service Manual).
2. Replace the compressor and balance the PAG lubricant in the system following the procedures in the vehicle service manual.
3. Install an in-line filter in the liquid line after the condenser and before the "Y" in the line separating the front and rear systems.
4. Remove, inspect and clean the orifice tube for the front system. It is located in the liquid line after the "Y" joint.
5. Replace the orifice tube.
6. Disconnect seat belt and remove rear bench seat.
7. Remove the right second passenger seat shoulder belt retainer from the right side C-pillar.
8. Remove the (5) screws from the right side C-pillar trim.
9. Remove the (2) screws securing the right side lower trim panel to the C-pillar.
10. Remove the (5) screws securing the D-pillar covers.
11. Lift the right side lower trim panel and roll forward to remove, this exposes the rear HVAC evaporator case module.
