GMCSID
08-03-2004, 12:17 PM
<H1>Poor A/C Performance - A/C Will Not Blow Cold Enough (Perform A/C System Checks, Replace Accumulator, If Necessary) #02-01-38-007C - (Jul 27, 2004)</H1>Poor A/C Performance -- A/C Will Not Blow Cold Enough (Perform A/C System Checks, Replace Accumulator if Necessary)
2002-2004 Chevrolet Silverado
2002-2004 GMC Sierra
with 6.6L Diesel Engine (VINs 1, 2 -- RPOs LB7, LLY)
and Denso A/C Compressor
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).<A name=ss1-1539443><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1539443&evc=numSrch#ss1-1539443" target="_blank">
<H5>Condition</A></H5>
Some customers may comment on less than desirable A/C performance, especially when the ambient temperature is above 32°C (90°F).<A name=ss2-1539443><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1539443&evc=numSrch#ss2-1539443" target="_blank">
<H5>Correction</A></H5>
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.
<UL ="BULLET">
<LI>Check for A/C system leaks.
<LI>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.
<LI>If no leaks were found and the A/C system is charged to specification, replace the accumulator using the procedure listed below. </LI>[/list]
If normal diagnostics do not lead to a correction, then perform the following A/C system checks.
[list=1]
<LI ="1">Re-calibrate the actuators. Refer to Recalibrating Actuators in the HVAC System - Manual/Automatic sub-section of the Service Manual (SI Document ID #904666).
<LI ="1">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.
<LI ="1">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).
<LI ="1">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.
<LI ="1">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).
<LI ="1">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.
<H4>Important</H4>
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.
<LI
2002-2004 Chevrolet Silverado
2002-2004 GMC Sierra
with 6.6L Diesel Engine (VINs 1, 2 -- RPOs LB7, LLY)
and Denso A/C Compressor
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).<A name=ss1-1539443><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1539443&evc=numSrch#ss1-1539443" target="_blank">
<H5>Condition</A></H5>
Some customers may comment on less than desirable A/C performance, especially when the ambient temperature is above 32°C (90°F).<A name=ss2-1539443><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1539443&evc=numSrch#ss2-1539443" target="_blank">
<H5>Correction</A></H5>
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.
<UL ="BULLET">
<LI>Check for A/C system leaks.
<LI>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.
<LI>If no leaks were found and the A/C system is charged to specification, replace the accumulator using the procedure listed below. </LI>[/list]
If normal diagnostics do not lead to a correction, then perform the following A/C system checks.
[list=1]
<LI ="1">Re-calibrate the actuators. Refer to Recalibrating Actuators in the HVAC System - Manual/Automatic sub-section of the Service Manual (SI Document ID #904666).
<LI ="1">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.
<LI ="1">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).
<LI ="1">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.
<LI ="1">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).
<LI ="1">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.
<H4>Important</H4>
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.
<LI