GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

  1. Disconnect the rear window defogger relay.
  2. Turn the ignition switch on.
  3. Using a test light, probe between B+ and the rear window defogger relay connector terminal C5.

Is the test light on?

--

Go to Step 4

Go to Step 2

2

Using a test light, probe between the rear window defogger relay connector terminal B5 and ground.

Is the test light on?

--

Go to Step 7

Go to Step 3

3

Replace the rear window defogger relay. Rear Window Defogger Relay Replacement

Is the repair complete?

--

Go to Defogger System Check

--

4

Check for a short to ground in CKT 193.

Is there a short to ground in CKT 193?

--

Go to Step 5

Go to Step 6

5

Repair the short to ground in CKT 193.

Is the repair complete?

--

Go to Defogger System Check

--

6

Replace the A/C-heater control. Refer to Control Assembly Replacement in HVAC Systems with A/C - Manual.

Is the repair complete?

--

Go to Defogger System Check

--

7

Repair short to B+ in CKT 293.

Is the repair complete?

--

Go to Defogger System Check

--