Schematic Reference: Defogger Schematics

Connector End View Reference: Stationary Windows Connector End Views

Did you perform the Defogger Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Defogger

1. Start the engine.
2. Depress the rear window defogger switch.
3. Observe the rear window defogger indicator on the HVAC control assembly.

Does the rear window defogger indicator illuminate?

Go to Step 3

Go to Step 11

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

Does the test lamp illuminate?

Go to Step 4

Go to Step 5

Connect a test lamp between the switched side of the rear window defogger grid and the ground 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 15

5

Command the rear defog relay ON and OFF, by depressing the rear window defogger switch.

Do you hear a click when you command the Rear Defog relay ON and OFF?

Go to Step 8

Go to Step 6

1. Turn OFF the ignition.
2. Disconnect the Rear Defog relay.
3. Start the engine.
4. Connect a test lamp between the supply voltage circuit of the Rear Defog relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 10

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

Does the test lamp illuminate?

Go to Step 13

Go to Step 11

1. Turn OFF the ignition.
2. Disconnect the Rear Defog relay.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between the battery positive voltage circuit of the Rear Defog relay switched input and a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 16

1. Connect a 30 amp fused jumper between the battery positive voltage circuit of the Rear Defog relay switched input and the relay switched output to the supply voltage circuit of the rear window defogger grid.
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 17

Test the supply voltage circuit of the Rear Defog relay coil for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 14

Test the control circuit of the Rear Defog relay for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 12

Inspect for poor connections at the harness connector of the HVAC control assembly. 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 21

Go to Step 18

Inspect for poor connections at the Rear Defog 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 21

Go to Step 19

Inspect for poor connections at the harness connector of the body control module (BCM). 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 21

Go to Step 20

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

Did you complete the repair?

Go to Step 21

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Repair an open or short to ground in the battery positive voltage circuit of the Rear Defog relay switched input. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 21

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Repair an open or a 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 21

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Replace the HVAC control assembly. Refer to HVAC Control Module Replacement in HVAC Systems - Manual.

Did you complete the replacement?

Go to Step 21

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Replace the Rear Defog relay.

Did you complete the replacement?

Go to Step 21

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Important: Perform the setup procedure for the BCM.

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 21

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2