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Makes 🢒 Chevrolet 🢒 2000 🢒 Chevy C Silverado - 2WD 🢒 Body and Accessories 🢒 Doors 🢒 Rear Window Defogger Inoperative

Rear Window Defogger Inoperative w/o E52

Test Description

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

  1. Listen for an audible click when the rear window defogger relay operates. Command both the ON and OFF states of the rear window defogger relay. Repeat the commands as necessary.

Step

Action

Yes

No

SCHEMATIC REFERENCE: Defogger Schematics

1

Did you review the Rear Window Defogger operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms

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 4

3

Connect a test lamp between the left side of the rear window defogger grid and the right side of the rear window defogger grid.

Does the test lamp illuminate?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 6

4
  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the HVAC Control Module.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ignition 3 voltage circuit of the HVAC Control Module and a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 15

5

Connect a test lamp between the ignition 3 voltage circuit of the HVAC control module and the ground circuit of the HVAC control module.

Does the test lamp illuminate?

Go to Step 14

Go to Step 16

6

Command the rear defogger relay ON and OFF, by depressing the rear defogger switch on the HVAC Control Module.

Do you hear a click when you command the rear defogger relay ON and OFF?

Go to Step 9

Go to Step 7

7
  1. Turn OFF the ignition.
  2. Disconnect the rear window defogger relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ignition 1 voltage circuit of the rear window defogger 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 rear window defogger relay coil and the control circuit of the rear window defogger relay.
  2. Depress the rear window defogger switch.

Does the test lamp illuminate?

Go to Step 13

Go to Step 12

9
  1. Turn OFF the ignition.
  2. Disconnect the rear window defogger relay.
  3. Connect a test lamp between the battery positive voltage circuit of the rear window defogger relay switch and a good ground.

Does the test lamp illuminate?

Go to Step 10

Go to Step 18

10
  1. Connect a 30 amp fused jumper wire between the battery positive voltage circuit of the rear window defogger relay switch and the supply voltage circuit of the rear window defogger grid.
  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.

Does the test lamp illuminate?

Go to Step 13

Go to Step 11

11

Connect a test lamp between the rear window defogger grid and a good ground.

Does the test lamp illuminate?

Go to Step 20

Go to Step 19

12

Test the control circuit of the rear window defogger relay for an open or short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 23

Go to Step 14

13

Inspect for a poor connection at the rear window defogger relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 23

Go to Step 21

14

Inspect for a poor connection at the harness connector of the HVAC Control Module. Refer Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 23

Go to Step 22

15

Repair an open or short to ground in the ignition 3 voltage circuit of the HVAC Control Module. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 23

--

16

Repair an open or high resistance in the ground circuit of the HVAC Control Module. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 23

--

17

Repair an open or high resistance in the ignition 1 voltage circuit of the rear window defogger relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 23

--

18

Repair an open or high resistance in the battery positive voltage circuit of the rear window defogger relay switch. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 23

--

19

Repair an open or short to ground in the supply voltage circuit of the rear window defogger grid. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 23

--

20

Repair an open or high resistance in the ground circuit of the rear window defogger grid. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 23

--

21

Replace the rear window defogger relay.

Did you complete the replacement?

Go to Step 23

--

22

Replace the HVAC Control Module. Refer to Control Assembly Replacement in HVAC Systems - Manual or Control Assembly Replacement in HVAC Systems - Automatic.

Did you complete the replacement?

Go to Step 23

--

23

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2

Rear Window Defogger Inoperative w/ E52

Test Description

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

  1. Listen for an audible click when the rear window defogger relay operates. Command both the ON and OFF states of the rear window defogger relay. Repeat the commands as necessary.

Step

Action

Yes

No

SCHEMATIC REFERENCE: Defogger Schematics

1

Did you review the Rear Window Defogger operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms

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 indicator illuminate?

Go to Step 3

Go to Step 6

3
  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 LR 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 RR cargo door.

Does the test lamp illuminate on both rear window defogger grids?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 4

4

Does the test lamp illuminate on one of the rear window defogger grids?

Go to Step 5

Go to Step 8

5

Connect a test lamp between the inoperative rear window defogger grid and a good ground.

Does the test lamp illuminate?

Go to Step 22

Go to Step 21

6
  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the HVAC Control Module.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ignition 3 voltage circuit of the HVAC Control Module and a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 17

7

Connect a test lamp between the ignition 3 voltage circuit of the HVAC Control Module and the ground circuit of the HVAC Control Module.

Does the test lamp illuminate?

Go to Step 16

Go to Step 18

8

Command the rear defogger relay ON and OFF, by depressing the rear defogger switch on the HVAC Control Module.

Do you hear a click when you command the rear defogger relay ON and OFF?

Go to Step 11

Go to Step 9

9
  1. Turn OFF the ignition.
  2. Disconnect the rear window defogger relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ignition 1 voltage circuit of the rear window defogger relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 10

Go to Step 19

10
  1. Connect a test lamp between the ignition 1 voltage circuit of the rear window defogger relay coil and the control circuit of the rear window defogger relay.
  2. Depress the rear window defogger switch.

Does the test lamp illuminate?

Go to Step 15

Go to Step 14

11
  1. Turn OFF the ignition.
  2. Disconnect the rear window defogger relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the battery positive voltage circuit of the rear window defogger relay switch and a good ground.

Does the test lamp illuminate?

Go to Step 12

Go to Step 20

12
  1. Connect a 30 amp fused jumper wire between the battery positive voltage circuit of the rear window defogger relay switch and the supply voltage circuit of the rear window defogger grid.
  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.

Does the test lamp illuminate?

Go to Step 15

Go to Step 13

13

Connect a test lamp between the rear window defogger grid and a good ground.

Does the test lamp illuminate?

Go to Step 22

Go to Step 21

14

Test the control circuit of the rear window defogger relay for an open or short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 16

15

Inspect for a poor connection at the rear window defogger relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 23

16

Inspect for a poor connection at the harness connector of the HVAC Control Module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 24

17

Repair an open or short to ground in the ignition 3 voltage circuit of the HVAC Control Module. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 25

--

18

Repair an open or high resistance in the ground circuit of the HVAC Control Module. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 25

--

19

Repair an open or high resistance in the ignition 1 voltage circuit of the rear window defogger relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 25

--

20

Repair an open or high resistance in the battery positive voltage circuit of the rear window defogger relay switch. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 25

--

21

Repair an open or short to ground in the supply voltage circuit of the rear window defogger grid. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 25

--

22

Repair an open or high resistance in the ground circuit of the rear window defogger grid. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 25

--

23

Replace the rear window defogger relay.

Did you complete the replacement?

Go to Step 25

--

24

Replace the HVAC Control Module. Refer to Control Assembly Replacement in HVAC Systems - Manual or Control Assembly Replacement in HVAC Systems - Automatic.

Did you complete the replacement?

Go to Step 25

--

25

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2