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

Step

Action

Value(s)

Yes

No

1

Did you perform the Defogger System Check?

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Go to Step 2

Go to Defogger System Check

2
  1. Turn the ignition switch to the RUN position.
  2. Press and release the rear defogger switch.
  3. Observe if the defogger ON indicator turns ON.

Does the defogger ON indicator turn ON?

--

Go to Step 3

Go to Step 16

3
  1. Remove the rear window defogger relay.
  2. Use a test lamp to backprobe the rear window defogger relay harness connector between terminals A 2 and C 1.

Does the test lamp light?

--

Go to Step 4

Go to Step 9

4

Use a test lamp to backprobe the rear window defogger relay harness connector between terminal C 2 and ground.

Does the test lamp light?

--

Go to Step 5

Go to Step 8

5
  1. Press and release the rear defogger switch again if the rear defogger ON indicator turns OFF before the test is complete.
  2. Use a test lamp to backprobe the rear window defogger relay harness connector between terminals C 2 and A 1.

Does the test lamp light?

--

Go to Step 6

Go to Step 7

6

Inspect for loose terminals at the relay connector and repair if found. If no loose connections are found, replace the defogger relay.

Is the repair complete?

--

Go to Defogger System Check

--

7
  1. Repair a poor connection or an open in CKT 292 (LT BLU).
  2. Inspect the system.

Is the repair complete?

--

Go to Defogger System Check

--

8
  1. Repair a poor connection or an open in CKT 41 (BRN) between the rear window defogger relay harness connector terminal C 2 and the fuse block terminal D 10.
  2. Inspect the system.

Is the repair complete?

--

Go to Defogger System Check

--

9
  1. Press and release the rear defogger switch again if the rear defogger ON indicator turns OFF before the test is complete.
  2. Use a test lamp to backprobe the rear window defogger relay harness connector between terminal A 2 and ground.

Does the test lamp light?

--

Go to Step 10

Go to Step 15

10
  1. Press and release the rear defogger switch again if the rear defogger ON indicator turns OFF before the test is complete.
  2. Use a test lamp to backprobe the rear defogger grid harness connector between CKT 293 (PPL) and CKT 850 (BLK).

Does the test lamp light ?

--

Go to Step 11

Go to Step 12

11
  1. Repair the rear defogger grid. Refer to Grid Line Repair .
  2. Inspect the system.

Is the repair complete?

--

Go to Defogger System Check

--

12
  1. Press and release the rear defogger switch again if the rear defogger ON indicator turns OFF before the test is complete.
  2. Use a test lamp to backprobe the rear defogger grid harness connector between CKT 293 (PPL) and ground.

Does the test lamp light?

--

Go to Step 13

Go to Step 14

13
  1. Repair a poor connection or an open in CKT 850 (BLK) between the rear defogger grid and G 301.
  2. Inspect the system.

Is the repair complete?

--

Go to Defogger System Check

--

14
  1. Repair a poor connection or an open in CKT 293 (PPL) between the rear window defogger relay connector terminal C 1 and the rear defogger grid connector.
  2. Inspect the system.

Is the repair complete?

--

Go to Defogger System Check

--

15
  1. Repair a poor connection or an open in CKT 1040 (ORN) between the fuse block terminal A 2 and the rear window defogger relay harness connector terminal A 2.
  2. Inspect the system.

Is the repair complete?

--

Go to Defogger System Check

--

16

Inspect Fuse 4 in the fuse block for an open.

Is the fuse open?

--

Go to Step 17

Go to Step 18

17
  1. Repair the short to ground in CKT 41 (BRN).
  2. Reinspect the system.

Is the repair complete?

--

Go to Defogger System Check

--

18
  1. Turn the ignition switch to the RUN position.
  2. Use a test lamp to backprobe the heater-A/C control connector C 2 terminals B 7 and B 8.

Does the test lamp light?

--

Go to Step 19

Go to Step 21

19
  1. Press and release the rear defogger switch.
  2. Use a test lamp to backprobe between the heater-A/C control connector C 2 terminal B 2 and ground.

Does the test lamp light?

--

Go to Step 20

Go to Step 24

20
  1. Repair a short to B+ in CKT 292 (LT BLU).
  2. Inspect the system.

Is the repair complete?

--

Go to Defogger System Check

--

21
  1. Use a test lamp to backprobe between the heater-A/C control harness connector C 2 terminal B 7 and ground.
  2. Retest the system.

Does the test lamp light?

--

Go to Step 22

Go to Step 23

22
  1. Repair a poor connection or an open in CKT 150 (BLK) between the heater-A/C control harness connector C 2 terminal B 7 and G 205.
  2. Inspect the system.

Is the repair complete?

--

Go to Defogger System Check

--

23
  1. Repair a poor connection or an open in CKT 41 (BRN) between the fuse block terminal D 10 and the heater-A/C control harness connector C 2 terminal B 7.
  2. Inspect the system.

Is the repair complete?

--

Go to Defogger System Check

--

24

Replace the heater-a/c control. Refer to Control Assembly Replacement in HVAC Systems.

Is the repair complete?

--

Go to Defogger System Check

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