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 rear window defogger system operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Stationary Windows

1. Turn ON the ignition, with the engine OFF.
2. Press 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 7

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 24

5

Command the DEFROST relay ON and OFF, by pressing the rear defogger switch on the HVAC control assembly.

Does the DEFROST relay click when you turn the rear defogger ON and OFF?

Go to Step 6

Go to Step 9

Command the REAR DEFOGGER relay ON and OFF, by pressing the rear defogger switch on the HVAC control assembly.

Does the REAR DEFOGGER relay click when you turn the rear defogger ON and OFF?

Go to Step 11

Go to Step 10

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

Does the test lamp illuminate?

Go to Step 8

Go to Step 22

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

Does the test lamp illuminate?

Go to Step 21

Go to Step 23

1. Turn OFF the ignition.
2. Remove the DEFROST relay from the rear fuse block. Refer to Relay Replacement in Wiring Systems.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between the ignition voltage circuit of the DEFROST relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 13

Go to Step 29

1. Turn OFF the ignition.
2. Remove the REAR DEFOGGER relay from the rear relay block. Refer to Relay Replacement in Wiring Systems.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between the ignition voltage circuit of the REAR DEFOGGER relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 14

Go to Step 12

1. Turn OFF the ignition.
2. Remove the REAR DEFOGGER relay from the rear relay block. Refer to Relay Replacement in Wiring Systems.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between the ignition voltage circuit of the REAR DEFOGGER relay switch and a good ground.

Does the test lamp illuminate?

Go to Step 16

Go to Step 18

1. Turn OFF the ignition.
2. Remove the DEFROST relay from the rear fuse block. Refer to Relay Replacement in Wiring Systems.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between the ignition voltage circuit of the DEFROST relay switch and a good ground.

Does the test lamp illuminate?

Go to Step 15

Go to Step 29

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

Does the test lamp illuminate?

Go to Step 19

Go to Step 17

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

Does the test lamp illuminate?

Go to Step 20

Go to Step 25

Test the control circuit of the REAR DEFOGGER relay 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 30

Go to Step 19

Test the control circuit of the rear defogger grid 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 30

Go to Step 20

Test the control circuit of the DEFROST relay 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 30

Go to Step 21

Test the voltage supply circuit of the REAR DEFOGGER relay switch 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 30

Go to Step 29

Inspect for a poor connection at the DEFROST 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 30

Go to Step 26

Inspect for a poor connection at the REAR 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 30

Go to Step 27

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 30

Go to Step 28

Repair the open or short to ground in the ignition voltage circuit of the HVAC control assembly. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 30

--

Repair the open or high resistance in the ground circuit of the HVAC control assembly. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 30

--

Repair the 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 30

--

Repair the open or high resistance in the ground circuit of the REAR DEFOGGER relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 30

--

Replace the DEFROST relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 30

--

Replace the REAR DEFOGGER relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 30

--

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

Did you complete the replacement?

Go to Step 30

--

Replace the rear fuse block. Refer to Master Electrical Component List in Wiring Systems.

Did you complete the replacement?

Go to Step 30

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2