Schematic Reference: Defogger Schematics

Did you review the operation rear window defogger 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 indicator illuminate?

Go to Step 3

Go to Step 6

1. Connect a test lamp between the left rear window defogger grid and a good ground.
2. Connect a test lamp between the right rear window defogger grid and a good ground.

Does the test lamp illuminate on both rear window defogger grids?

Go to Step 4

Go to Step 5

1. Connect a test lamp between the left side of the left rear window defogger grid and the right side of the left rear window defogger grid.
2. Connect a test lamp between the left side of the right rear window defogger grid and the right side of the right rear window defogger grid.

Does the test lamp illuminate on both rear window defogger grids?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 19

Does the test lamp illuminate on one of the rear window defogger grids?

Go to Step 20

Go to Step 9

1. Turn OFF the ignition.
2. Disconnect the harness connector C2 of the HVAC Control Assembly.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between battery positive voltage circuit, terminal A of the HVAC Control Assembly and a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 14

Connect a test lamp between the ignition voltage circuit, terminal B of the HVAC Control Assembly and a good ground.

Does the test lamp illuminate?

Go to Step 8

Go to Step 21

Connect a test lamp between the ignition voltage circuit and the ground circuit, terminal C of the HVAC Control Assembly.

Does the test lamp illuminate?

Go to Step 17

Go to Step 22

9

Command the Rear Window Defogger 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 Rear Window Defogger relay ON and OFF?

Go to Step 12

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 supply voltage circuit of the Rear Window Defogger relay coil and a good ground.
5. Depress the rear window defogger switch.

Does the test lamp illuminate?

Go to Step 11

Go to Step 15

Connect a test lamp between the supply voltage circuit and the ground circuit of the Rear Window Defogger relay coil.

Does the test lamp illuminate?

Go to Step 18

Go to Step 24

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 13

Go to Step 16

1. Connect a 25 amp fused jumper wire 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 18

Go to Step 20

Test the battery positive voltage circuit of the HVAC Control Assembly 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 28

Go to Step 23

Test the supply voltage circuit of the Rear Window Defogger relay coil 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 28

Go to Step 17

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 28

Go to Step 25

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 28

Go to Step 26

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 28

Go to Step 27

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 28

--

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 28

--

Repair an open or high resistance 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 28

--

Repair an 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 28

--

Repair the short to ground in the supply voltage circuit of the Rear Window Defogger relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

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

Did you complete the repair?

Go to Step 28

--

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 28

--

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 28

--

Replace the Rear Window Defogger relay.

Did you complete the replacement?

Go to Step 28

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2