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 Module.

Does the rear window defogger indicator illuminate?

Go to Step 3

Go to Step 10

Connect a test lamp between 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 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 13

5

1. Select from the special functions, under Miscellaneous Test, the Rear Defogger from the HVAC Control Module output controls.
2. With a scan tool, command the RR DEFOG relay ON and OFF.

Do you hear a click when you command the RR DEFOG relay ON and OFF?

Go to Step 8

Go to Step 6

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 voltage circuit of the RR DEFOG relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 14

1. Connect a test lamp between the control circuit of the RR DEFOG relay and the ignition voltage circuit of the RR DEFOG relay coil.
2. With a scan tool, command the RR DEFOG relay ON.

Does the test lamp illuminate?

Go to Step 12

Go to Step 10

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 switched input and a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 15

1. Connect a 30 amp fused jumper between the battery positive voltage circuit of the RR DEFOG relay switched input and the relay switched output to 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 12

Go to Step 16

Test the control circuit of the RR 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 19

Go to Step 11

Inspect for poor connections 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 19

Go to Step 17

Inspect for poor connections at the RR 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 19

Go to Step 18

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 19

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Repair an open or high resistance in the ignition voltage circuit of the RR DEFOG relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

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Repair an open or high resistance in the battery positive voltage circuit of the RR DEFOG relay switched input. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

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

Did you complete the repair?

Go to Step 19

--

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

Did you complete the replacement?

Go to Step 19

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Replace the RR DEFOG relay.

Did you complete the replacement?

Go to Step 19

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2