GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you review the system operation and perform the necessary inspections?

--

Go to Step 2

Go to Symptoms - Stationary Windows

2

  1. Turn the ignition to the RUN position.
  2. Turn the rear defogger switch on.
  3. Observe the status of the defogger on indicator.

Does the rear defogger turn on?

--

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

Go to Step 3

3

Are both the defogger indicator and the defogger grid inoperative?

--

Go to Step 4

Go to Step 5

4

  1. Turn the ignition switch to the OFF position.
  2. Connect a test lamp between the HVAC control connector C4 terminals A and D. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 8

5

Is the defogger grid operative while the defogger indicator is inoperative?

--

Go to Step 18

Go to Step 6

6

  1. Connect a test lamp between the HVAC control connector C4 terminal B and ground. Refer to Circuit Testing in Wiring Systems.
  2. Press the rear defogger switch.

Does the test lamp illuminate?

--

Go to Step 12

Go to Step 18

7

  1. Connect a test lamp between the HVAC control connector C4 terminals C and D. Refer to Circuit Testing in Wiring Systems.
  2. Turn the ignition switch to the RUN position.

Does the test lamp illuminate?

--

Go to Step 17

Go to Step 11

8

Connect a test lamp between the HVAC control connector C4 terminal A and ground. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 10

9

Repair a poor connection or an open in the ground circuit of the HVAC control. Refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 19

--

10

Repair a poor connection or an open in the battery voltage circuit of the HVAC control. Refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 19

--

11

Repair a poor connection or an open in the ignition 3 voltage circuit of the HVAC control. Refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 19

--

12

Connect a test lamp between the supply voltage circuit of the rear defogger grid and the ground circuit of the rear defogger grid at the rear defogger grid connector. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 13

Go to Step 14

13

Replace the rear defogger grid. Refer to Rear Lift Window Replacement .

Did you complete the replacement?

--

Go to Step 19

--

14

Connect a test lamp between the supply voltage circuit of the rear defogger grid and ground. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 16

Go to Step 15

15

Repair a poor connection or an open in the supply voltage circuit of the rear defogger grid. Refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 19

--

16

Repair a poor connection or an open in the ground circuit of the rear defogger grid. Refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 19

--

17

Inspect for and repair a short to ground or an open in the supply voltage circuit of the rear defogger grid. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and repair a short or an open?

--

Go to Step 19

Go to Step 18

18

Replace the HVAC control. Refer to Control Assembly Replacement in HVAC Systems - Manual.

Did you complete the replacement?

--

Go to Step 19

--

19

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3