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1. Ignition ON, observe the scan tool Rear Defrost State parameter while pressing the rear window defogger switch. The parameter should change between On and Off. If the parameter does not change between the commanded states, replace the HVAC 2. Observe the operation of the rear window defogger indicator while pressing the rear window defogger switch. The indicator should turn ON or OFF each time the rear window If the indicator does not turn ON or OFF with each switch press, replace the HVAC 3. Command the rear window defogger ON and OFF with a scan tool. The rear window defogger should turn ON and OFF when changing between the commanded states. Circuit/System Testing 1. Ignition OFF, disconnect the REAR DEFOG relay. 2. Test for less than 1.0 ohm between the ground circuit terminal 85 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 does not illuminate between the control circuit terminal 87 and ground. If the test lamp illuminates, test the control circuit for a short to voltage. 4. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an 5. Ignition OFF, disconnect the X2 harness connector at the defogger grid. 6. Test for less than 5 ohms between the defogger grid ground circuit terminal A and ground. If greater than the specified range, test the ground circuit for an open/high resistance. 7. Connect the harness connector at the defogger grid. 8. Ignition ON, connect a 30A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the defogger grid is activated. If the defogger grid does not activate, test the control circuit for a short to ground or 9. Connect a test lamp between the control circuit terminal 86 and ground. 10. Command the defogger grid ON and OFF by pressing and depressing the rear defogger switch. The test lamp should turn ON and OFF when changing between the commanded If the test lamp is always ON, test the control circuit for a short to voltage. If the
2008 Chevrolet Silverado 1500 2008 ACCESSORIES & EQUIPMENT Fixed and Moveable Windows - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
circuit tests normal, replace the HVAC control module. If the test lamp is always OFF, test the control circuit for a short to ground or an 11. If all circuits test normal, test or replace the REAR DEFOG relay. Component Testing Relay Test 1. Ignition OFF, disconnect the rear defog relay. 2. Test for 60-180 ohms between terminals 85 and 86. If not within the specified range, replace the relay. 3. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 If not the specified value, replace the relay. 4. Install a 30-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 If greater than the specified range, replace the relay. Rear Window Defogger Grid Test 1. Ignition ON, turn on the rear window defogger. 2. Verify that a test lamp illuminates between each rear window defogger grid line and ground. The test lamp should be off when testing at the ground side of the grid and get If the test lamp remains bright at the middle of the grid line, test for an open between If the test lamp remains off at the middle of the grid line, test for an open between the Repair Procedures Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
2008 Chevrolet Silverado 1500 2008 ACCESSORIES & EQUIPMENT Fixed and Moveable Windows - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Rear Window Replacement Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Control Module References for HVAC control module replacement, setup, and POWER REAR SLIDING WINDOW 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 power sliding rear window motor is controlled from the sliding rear window switch through Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance Sliding Rear Window Relay 2 2 - - Sliding Rear Window Switch 1 1 - - Sliding Rear Window Relay 2 2 2 - Sliding Rear Window Motor 2 2 2 - Sliding Rear Window Relay - 2 2 - 1. Sliding Rear Window Switch Malfunction
2008 Chevrolet Silverado 1500 2008 ACCESSORIES & EQUIPMENT Fixed and Moveable Windows - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
de-energized state both motor control circuits will be closed to ground. When one of the relays is Reference Information Schematic Reference Moveable Window Schematics Connector End View Reference Component Connector End Views Description and Operation Power Windows 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 Verification Ignition ON, command the sliding rear window to OPEN/CLOSE by pressing the front and rear Circuit/System Testing 1. Ignition OFF, disconnect the harness connector at the sliding rear window switch. 2. Ignition ON, verify the test lamp illuminates between the accessory voltage circuit terminal A and ground. If the test lamp does not illuminate, test the accessory voltage circuit for a short to
2008 Chevrolet Silverado 1500 2008 ACCESSORIES & EQUIPMENT Fixed and Moveable Windows - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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