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Home >> GMC >> 2002 >> Yukon Denali >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Heated Glass/Defoggers >> Stationary Window System >> Diagnostic Information and Procedures >> Defogger Inoperative - Rear Window (w/Cargo Doors) >> Test Description

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. 6:  Listen for an audible click when the RR DEFOG relay operates. Command both the ON and OFF states of the RR DEFOG relay. Repeat the commands as necessary.
Defogger Inoperative - Rear Window (w/Cargo Doors)

Step Action Yes No
Schematic Reference: Defogger Schematics 
1 Did you review the operation of the rear window defogger system and perform the necessary inspections? Go to Step 2  Go to Symptoms - Stationary Windows 
2
  1. Turn ON the ignition, with the engine OFF.
  2. Depress the rear window defogger switch.
  3. Observe the rear window defogger indicator on the HVAC Control Module.
Does the rear window defogger indicator illuminate?		 Go to Step 3  Go to Step 11 
3
  1. Connect a test lamp between the rear window defogger grid on the left cargo door and a good ground.
  2. Connect a test lamp between the rear window defogger grid on the right cargo door and a good ground.
Does the test lamp illuminate on both rear window defogger grids?		 Go to Step 4  Go to Step 5 
4
  1. Connect a test lamp between the left side of the rear window defogger grid and the right side of the rear window defogger grid on the left cargo door.
  2. Connect a test lamp between the left side of the rear window defogger grid and the right side of the rear window defogger grid on the right cargo door.
Does the test lamp illuminate on both rear window defogger grids?		 Go to TESTING FOR INTERMITTENT AND POOR CONNECTIONS Go to Step 15 
5 Does the test lamp illuminate on one of the rear window defogger grids? Go to Step 16  Go to Step 6 
6  Command the RR DEFOG relay ON and OFF, by depressing the rear window defogger switch on the HVAC Control Module.
Do you hear a click when you command the RR DEFOG relay ON and OFF?		 Go to Step 9  Go to Step 7 
7
  1. Turn OFF the ignition.
  2. Disconnect the RR DEFOG relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ignition 1 voltage circuit of the RR DEFOG relay coil and a good ground.
Does the test lamp illuminate?		 Go to Step 8  Go to Step 17 
8
  1. Connect a test lamp between the ignition 1 voltage circuit of the RR DEFOG relay coil and the control circuit of the RR DEFOG relay.
  2. Depress the rear window defogger switch.
Does the test lamp illuminate?		 Go to Step 13  Go to Step 11 
9
  1. Turn OFF the ignition.
  2. Disconnect the RR DEFOG relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the battery positive voltage circuit of the RR DEFOG relay switch and a good ground.
Does the test lamp illuminate?		 Go to Step 10  Go to Step 12 
10
  1. Connect a 30 amp fused jumper wire between the battery positive voltage circuit of the RR DEFOG relay switch and the supply voltage circuit of the rear window defogger.
  2. Connect a test lamp between the rear window defogger grid and a good ground.
Does the test lamp illuminate?		 Go to Step 13  Go to Step 16 
11 Test the control circuit of the RR DEFOG relay for an open or short to battery positive voltage. Refer to CIRCUIT TESTING and WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 21  Go to Step 14 
12 Test the battery positive voltage circuit of the RR DEFOG relay coil for an open or high resistance. Refer to CIRCUIT TESTING and WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 21  Go to Step 18 
13 Inspect for a poor connection at the RR DEFOG relay. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS .
Did you find and correct the condition?		 Go to Step 21  Go to Step 19 
14 Inspect for a poor connection at the harness connector of the HVAC Control Module. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS .
Did you find and correct the condition?		 Go to Step 21  Go to Step 20 
15 Repair an open or high resistance in the ground circuit of the rear window defogger grid. Refer to WIRING REPAIRS .
Did you complete the repair?		 Go to Step 21  -
16 Repair an open or high resistance in the supply voltage circuit of the rear window defogger. Refer to WIRING REPAIRS .
Did you complete the repair?		 Go to Step 21  -
17 Repair an open or high resistance in the ignition 1 voltage circuit of the RR DEFOG relay coil. Refer to WIRING REPAIRS .
Did you complete the repair?		 Go to Step 21  -
18 Repair the short to ground in the supply voltage circuit of the rear window defogger. Refer to WIRING REPAIRS .
Did you complete the repair?		 Go to Step 21  -
19 Replace the RR DEFOG relay.
Did you complete the replacement?		 Go to Step 21  -
20 Replace the HVAC Control Module. Refer to HVAC CONTROL ASSEMBLY for manual HVAC system or HVAC CONTROL MODULE REPLACEMENT for automatic HVAC system.
Did you complete the replacement?		 Go to Step 21  -
21 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 2 
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