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Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Verification 1. Engine running, press the A/C request switch. The A/C compressor clutch should engage. 2. Place the mode switch in the defrost position. The A/C compressor clutch should engage. If the clutch does not engage refer to Circuit/System Testing 1. Ignition OFF, disconnect the harness connector at the A/C low pressure switch. 2. Test for less than 5 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance. 3. Ignition ON, verify the scan tool Low Pressure Switch parameter is Open. If not the specified value, test the signal circuit terminal A for a short to ground. If the 4. Connect a 3-amp fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool Low Pressure Switch parameter is Closed. If not the specified value, test the signal circuit for a short to voltage or an open/high 5. Connect the harness connector at the A/C low pressure switch. Verify the scan tool Low Pressure Switch parameter is Closed. If not the specified value, test or replace the A/C low pressure switch. 6. Ignition OFF, disconnect the A/C relay. 7. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 and ground. If the test lamp illuminates, test the control circuit for a short to voltage. 8. Verify that a test lamp illuminates between the ignition circuit terminal 85 and ground.
2008 Chevrolet Silverado 1500 2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
If the test lamp does not illuminate, test the ignition circuit for a short to ground or a 9. Verify that a test lamp illuminates between the relay B+ circuit terminal 30 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or a 10. Disconnect the harness connector at the A/C clutch coil. 11. Test for less than 1 ohm between the ground circuit terminal 2 and ground. If greater than the specified range, test the ground circuit for an open/high resistance. 12. Connect the harness connector at the A/C clutch coil. 13. Connect a 10-amp fused jumper wire between the B+ circuit terminal 30 and control circuit terminal 87. Verify the A/C clutch is activated. If the A/C clutch does not activate, test the control circuit for an open/high resistance. 14. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86. 15. Command the A/C relay output function ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the If the test lamp is always OFF, test the control circuit for a short to voltage, or an 16. If all circuits test normal, test or replace the A/C clutch relay. Repair Procedures Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Air Conditioning Compressor Replacement (LY2, LY5, LH6, L76, L92 and LMG) or Compressor Clutch Plate/Hub Assembly Replacement (4.3L, 6.6L) or Compressor Control Module References for HVAC control module and ECM replacement, setup, and
2008 Chevrolet Silverado 1500 2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
BLOWER MOTOR MALFUNCTION Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. Diagnostic Fault Information Circuit/System Description The blower motor control module is an interface between the HVAC control module and the Reference Information Schematic Reference HVAC Schematics Connector End View Reference Component Connector End Views Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance Blower Motor Control 1 1 - - Blower Motor B+ 1 1 - - Blower Motor Speed Control 2 1 1 - Blower Motor Control 2 1 1 - Ground - 1 - - 1. Blower Motor Inoperative
2008 Chevrolet Silverado 1500 2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Description and Operation Air Delivery Description and Operation Air Temperature Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Testing 1. Ignition OFF, disconnect the X2 harness connector at the blower motor control module. 2. Test for less than 1.0 ohm between the ground circuit terminal 5 and ground. If greater than the specified range, test the ground circuit for an open/high resistance. 3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 6 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an 4. Connect a DMM between the control circuit terminal 3 and ground. 5. Cycle the blower motor from OFF to HIGH. The voltage should increase while changing between the commanded states. If voltage remains greater than 11.5 volts while changing between the commanded If voltage remains less than 1.0 volts while changing between the commanded states, If voltage is between 1.0-11.5 volts and does not increase when changing between the
2008 Chevrolet Silverado 1500 2008 HVAC HVAC - Manual - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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