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

Important: Make sure that the park or head lights are turned OFF. The backlighting will effect the illumination of the rear window defogger indicator.

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 12

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 14

5

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

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

Go to Step 8

Go to Step 6

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 voltage circuit of the Rear Window Defogger relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 15

1. Turn OFF the ignition.
2. Connect a test lamp between the control circuit of the Rear Window Defogger relay and the ignition voltage circuit of the Rear Window Defogger relay coil.
3. Turn ON the ignition, with the engine OFF.
4. With a scan tool, command the Rear Window Defogger relay ON.

Does the test lamp illuminate?

Go to Step 13

Go to Step 10

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 switched input and a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 11

1. Connect a 30 amp fused jumper between the battery positive voltage circuit of the Rear Window Defogger 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 13

Go to Step 17

Test the control circuit of the Rear Window Defogger 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 20

Go to Step 12

Test the battery positive voltage circuit of the Rear Window Defogger relay switched input for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 20

Go to Step 16

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 20

Go to Step 18

Inspect for poor connections 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 20

Go to Step 19

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 20

--

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

Did you complete the repair?

Go to Step 20

--

Repair the 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 20

--

Repair an open or high resistance 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 20

--

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

Did you complete the replacement?

Go to Step 20

--

Replace the Rear Window Defogger relay.

Did you complete the replacement?

Go to Step 20

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2

Schematic Reference: Defogger Schematics

Connector End View Reference: Stationary Windows Connector End Views

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

Important: Make sure that the park lamps or headlamps are turned OFF. The backlighting will affect the illumination of the rear window defogger indicator.

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 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 14

5

Command the rear window 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 window defogger relay ON and OFF?

Go to Step 8

Go to Step 6

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 voltage circuit of the rear window defogger relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 15

1. Connect a test lamp between the ignition 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 10

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 switched input and a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 11

1. Connect a 30-ampere fused jumper between the battery positive voltage circuit of the rear window defogger 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 control circuit of the rear window defogger 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 20

Go to Step 12

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

Did you find and correct the condition?

Go to Step 20

Go to Step 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 20

Go to Step 18

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 20

Go to Step 19

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 20

--

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

Did you complete the repair?

Go to Step 20

--

Repair the 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 20

--

Repair an open or high resistance 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 20

--

Replace the HVAC control module. Refer to Heater and Air Conditioning Control Replacement in HVAC Systems - Manual.

Did you complete the replacement?

Go to Step 20

--

Replace the rear window defogger relay.

Did you complete the replacement?

Go to Step 20

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2