<H1>Poor A/C Performance - A/C will not Blow Cold Enough (Perform A/C System Checks) #02-01-38-007A - (06/05/2003)</H1>
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Table 1:</TD>
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A/C Performance Table - 6.6L</TD></TR></T></TABLE>Poor A/C Performance -- A/C Will Not Blow Cold Enough (Perform A/C System Checks)
2003 Chevrolet Silverado
2003 GMC Sierra
with 6.6L Diesel Engine (VIN 1 -- RPO LB7)
This bulletin is being revised to update a temperature reading under Condition and to change the A/C Performance Table under Correction. Please discard Corporate Bulletin Number 02-01-38-007 (Section 01 -- HVAC).<A name=ss1-1341169><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1341169&evc=numSrch#ss1-1341169" target="_blank">
<H5>Condition</A></H5>
Some customers may comment on less than desirable A/C performance, especially when ambient temperature is above 32°C (90°F).<A name=ss2-1341169><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1341169&evc=numSrch#ss2-1341169" target="_blank">
<H5>Correction</A></H5>
If normal diagnostics do not lead to a correction, then perform the following A/C system checks.
<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.
<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). When recovering the A/C charge, recovery must be pulled for at least 45 minutes.
<LI =1>Check the low pressure cycling switch for proper operation. The low pressure switch opens at 148 kPa (21.5 psi), which stops compressor operation and closes when the low side pressure reaches 276 kPa (40 psi). This enables the compressor to turn back on.
<LI =1>When performing the refrigerant system performance test, refer to the updated specification chart listed below. </LI>
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<H4>A/C Performance Table - 6.6L</H4></A>
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Ambient Air Temperature</TH>
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Relative Humidity</TH>
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Service Port Pressure</TH>
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Maximum Discharge Air Temperature</TH></TR>
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Low Side </TH>
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High Side</TH></TR>
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13-18°C (55-65°F)</TD>
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0-100%</TD>
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150-279 kPa (22-41 psi)</TD>
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420-1140 kPa (61-165 psi)</TD>
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9°C (48°F)</TD></TR>
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19-24°C (66-75°F)</TD>
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Below 40%</TD>
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