GM Service Manual Online
For 1990-2009 cars only

Defoggers Are Always ON

Step

Action

Value(s)

Yes

No

1

  1. Disconnect the rear window defogger relay.
  2. Turn the ignition switch to the RUN position.
  3. Use a test lamp in order to probe between B+ and the rear window defogger relay connector terminal A 1 (CKT 193).

Does the test lamp light?

--

Go to Step 4

Go to Step 2

2

Use a test lamp in order to probe between the rear window defogger relay connector terminal A 2 (CKT 293) and ground.

Does the test lamp light?

--

Go to Step 7

Go to Step 3

3

  1. Replace the rear window defogger relay.
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

4

Inspect for a short to ground in CKT 193 (WHT).

Is there a short to ground on the circuit?

--

Go to Step 5

Go to Step 6

5

  1. Repair the short to ground in CKT 193 (WHT).
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

6

  1. Replace the heater-a/c control. Refer to Control Assembly Replacement for the manual HVAC system or;
  2. Refer to Control Assembly Replacement for the Automatic HVAC system.

Is the repair complete?

-

System OK

-

7

  1. Keep the test lamp connected in the same place.
  2. Remove the HEATED MIRROR fuse from the fuse block.

Does the test lamp light?

--

Go to Step 8

Go to Step 9

8

  1. Repair a short to B+ in CKT 293 (PPL).
  2. Inspect the system again.

Is the repair complete?

--

System OK

--

9

  1. Repair a short to B+ in CKT 267 (ORN).
  2. Inspect the system again.

Is the repair complete?

--

System OK

--