Schematic Reference: Defogger Schematics

Connector End View Reference: Stationary Windows Connector End Views

DEFINITION: The rear window defogger is completely inoperative. No part of the rear window is heated.

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

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 Assembly.

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

Go to Step 14

5

Command the RR DEFOG relay ON and OFF, by depressing the rear window defogger switch on the HVAC Control Assembly.

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 15

1. Connect a test lamp between the ignition 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 10

1. Turn OFF the ignition.
2. Disconnect the RR DEFOG relay.
3. 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 11

1. Connect a 30 amp fused jumper wire 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 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 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 20

Go to Step 12

Test the battery positive voltage circuit of the RR DEFOG relay switched input for an open or high resistance. 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 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 20

Go to Step 18

Inspect for a poor connection 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 20

Go to Step 19

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

Did you complete the repair?

Go to Step 20

--

Repair a short to ground in the supply voltage circuit of the rear 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 defogger grid. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 20

--

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

Did you complete the replacement?

Go to Step 20

--

Replace the RR DEFOG 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