Subject:
Poor A/C Performance — A/C Will Not Blow Cold Enough (Perform A/C System Checks, Replace Accumulator if Necessary)
Models:
2002–2004 Chevrolet Silverado
2002–2004 GMC Sierra
with 6.6L Diesel Engine (VINs 1, 2 — RPOs LB7, LLY)
and Denso A/C Compressor
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This bulletin is being revised to add part numbers for the hose, bracket and insulator to the Parts Information. Please discard Corporate Bulletin Number 02-01-38-007B (Section 01 — HVAC).
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Condition
Some customers may comment on less than desirable A/C performance, especially when the ambient temperature is above 32°C (90°F).
Correction
Perform the following A/C system checks and replace the accumulator with P/N 89018601, if necessary. This new accumulator requires the accumulator bracket, the accumulator insulator and the A/C suction hose to be replaced also.
•Check for A/C system leaks.
•Check the A/C system for proper refrigerant charge. This requires recovering the refrigerant to determine charge in system. Refer to Refrigerant Recovery and Recharging in the HVAC sub-section of the Service Manual.
•If no leaks were found and the A/C system is charged to specification, replace the accumulator using the procedure listed below.
If normal diagnostics do not lead to a correction, then perform the following A/C system checks.
•Re-calibrate the actuators. Refer to Recalibrating Actuators in the HVAC System – Manual/Automatic sub-section of the Service Manual (SI Document ID #904666).
•Inspect the lower A/C condenser deflector for proper installation. The deflector should be positioned at the lower part of the condenser and extend forward into the top of the front bumper and below the two fresh air intake holes.
•Check the engine cooling fan clutch for proper operation. Refer to Fan Clutch Diagnosis in the Engine Cooling sub-section of the Service Manual (SI Document ID #774320).
•If the vehicle is equipped with a front license plate, inspect for proper installation. If the license plate bracket is installed upside down, it will block part of the two fresh air intake holes in the bumper. When the license plate bracket is installed correctly, the writing on the back of the bracket will be upside down.
Inspect for material between the radiator and condenser. Remove the top plate to confirm that there is no restriction. A radiator front filled with material will decrease condenser performance.
•Some improvements have been found by lowering the A/C charge from 0.82 kg (1.8 lbs) to 0.73 kg (1.6 lbs).
•Check the low pressure cycling switch for proper operation. The low pressure switch opens at 172–234 kPa (25–34 psi) , which stops compressor operation and closes when the low side pressure reaches 276–310 kPa (40–45 psi). This enables the compressor to turn back on.
Important: Compressor clutch engagement cannot be used to determine the status of the low pressure switch. The low pressure switch is one of several inputs to the HVAC control module for A/C request authorization. A/C request is one of several inputs to the powertrain control module (PCM) that control A/C compressor clutch engagement.
Using a scan tool to monitor low pressure switch status while monitoring the low side pressure with the ACR 2000 at the service port and watch the pressure at which the switch opens/closes is imperative to successfully diagnosing the switch.
•If the A/C performance has not improved after performing the above steps, replace the accumulator with P/N 89018601, using the procedure listed below. This new accumulator also requires the accumulator bracket, accumulator insulator and A/C suction hose to be replaced.
Accumulator Replacement
•Remove the suction hose mounting bolt from the A/C compressor.
•Remove the suction hose from the compressor.
•Remove the suction hose nut from the accumulator.
•Remove the suction hose from the accumulator.
•Remove the evaporator tube nut from the evaporator.
•Remove the evaporator tube from the evaporator.
•Disconnect the electrical connector from the A/C low pressure switch.
•Remove the nut from the evaporator fitting.
•Remove the accumulator bracket nut from the retaining stud.
•Remove the accumulator.
•Remove the retaining bracket bolt. This bolt must be reused for the new bracket.
•Remove the insulator. One half of the insulator must be reused.
•Install the new insulator and one half of the old insulator onto the new accumulator.
•Install the new retaining bracket and bolt to the accumulator. Do not tighten at this time.
•Add the PAG oil directly into the new accumulator that was removed during the recovery process plus an additional 90 ml (3 oz).
•Install the new accumulator.
•Install the accumulator bracket nut.
Tighten
Tighten the nut to 9 [n-m] (80 lb in).
•Tighten the retaining bracket bolt.
Tighten
Tighten the nut to 10 [n-m] (89 lb in).
•Install the nut to the evaporator fitting.
Tighten
Tighten the nut to 16 [n-m] (12 lb ft).
•Install the evaporator tube to the evaporator.
•Install the evaporator tube nut to the evaporator.
Tighten
Tighten the nut to 16 [n-m] (12 lb ft).
•Install the new suction hose to the accumulator.
•Install the suction hose nut to the accumulator.
Tighten
Tighten the nut to 16 [n-m] (12 lb ft).
•Connect the electrical connector to the A/C low pressure switch.
•Install the new suction hose to the compressor.
•Install the suction hose mounting bolt to the A/C compressor.
Tighten
Tighten the bolt to 16 [n-m] (12 lb ft).
Parts Information
*This a unique Labor Operation Number for use only with this bulletin. This number will not be published in the Labor Time Guide.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
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