GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1998 🢒 Grand Prix 🢒 Body and Accessories 🢒 Stationary Windows 🢒 Rear Window Defogger Inoperative

Step

Action

Value(s)

Yes

No

1
  1. Turn the ignition switch to the RUN position.
  2. Press and release the rear defogger switch.
  3. Inspect to see if the defogger ON indicator comes on.

Does the indicator turn on?

--

Go to Step 2

Go to Step 15

2
  1. Remove the rear window defogger relay.
  2. Use a test lamp in order to probe the rear window defogger relay harness connector between terminal A2 and terminal C1.

Does the test lamp light?

--

Go to Step 3

Go to Step 8

3

Use a test lamp in order to backprobe the rear window defogger relay harness connector between terminal C2 and ground.

Does the test lamp light?

--

Go to Step 4

Go to Step 7

4
  1. If the rear defogger ON indicator turns off before the test is made, press and release the rear defogger switch again.
  2. Use a test lamp in order to backprobe the rear window defogger relay harness connector between terminal A1 and terminal C2.

Does the test lamp light?

--

Go to Step 5

Go to Step 6

5

Replace the rear window defogger relay.

Is the repair complete?

--

System OK

--

6
  1. Repair a poor connection or an open in CKT 193 (WHT).
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

7
  1. Repair a poor connection or an open in CKT 541 (BRN) between the rear window defogger relay harness connector terminal C2 and the fuse block terminal B2.
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

8
  1. If the rear defogger ON indicator turns off before the test is made, press and release the rear defogger switch again.
  2. Use a test lamp in order to backprobe the rear window defogger relay harness connector between terminal C1 and ground.

Does the test lamp light?

--

Go to Step 9

Go to Step 14

9
  1. Reinstall the rear window defogger relay.
  2. If the rear defogger ON indicator turns off before the test is made, press and release the rear defogger switch again.
  3. Use a test lamp in order to probe between the rear defogger grid harness connector C1 and connector C2.

Does the test lamp light?

--

Go to Step 10

Go to Step 11

10

Repair the rear defogger grid. Refer to Rear Window Defogger Braided Lead Wire .

Is the repair complete?

--

System OK

--

11
  1. If the rear defogger ON indicator turns off before the test is made, press and release the rear defogger switch again.
  2. Use a test lamp in order to probe between the rear defogger grid harness connector C1 and ground.

Does the test lamp light?

--

Go to Step  12

Go to Step 13

12
  1. Repair a poor connection or an open in CKT 750 (BLK) between the rear defogger grid connector C2 and G301.
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

13
  1. Repair a poor connection or an open in CKT 293 (PPL) between the rear window defogger relay connector terminal A2 and the rear defogger grid connector grid connector C1.
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

14
  1. Repair a poor connection or an open in CKT 1040 (ORN) between the fuse block terminal G2 and the rear window defogger relay harness connector terminal C1.
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

15

Inspect to see if the DIC/HVAC fuse (fuse 4) in the fuse block is open.

Is the fuse open?

--

Go to Step 16

Go to Step 17

16
  1. Repair the short to ground in CKT 541 (BRN).
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

17
  1. Turn the ignition switch to the RUN position.
  2. Use a test lamp in order to backprobe the heater-A/C control between connector terminal C1 and terminal C1 (CJ2) or between connector C 2 terminal C and terminal K (C60).

Does the test lamp light?

--

Go to Step 18

Go to Step 20

18
  1. Press and release the rear defogger switch.
  2. Use a test lamp in order to backprobe between the heater-A/C control harness connector terminal D15 (CJ2) or between connector C2 terminal D (C60) and ground.

Does the test lamp light?

--

Go to Step 19

Go to Step 23

19
  1. Repair a short to B+ in CKT 193 (WHT).
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

20

Use a test lamp in order to backprobe between the heater-A/C control harness connector terminal C5 (CJ2) or between connector C 2 terminal C (C60) and ground.

Does the test lamp light?

--

Go to Step 21

Go to Step 22

21
  1. Repair a poor connection or an open in CKT 150 (BLK) between the heater and A/C control harness connector terminal C1 (CJ2) or between connector C2 terminal K (C60) and G205.
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

22
  1. Repair a poor connection or an open in CKT 541 (BRN) between the fuse block terminal B2 and the heater and A/C control harness connector terminal C5 (CJ2) or between connector C 2 terminal C (C60) and ground.
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

23

Replace the heater - A/C control:

    • Refer to Control Assembly Replacement for Manual HVAC Systems
    • Refer to Control Assembly Replacement for Automatic HVAC Systems.

Is the repair complete?

--

System OK

--