GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Inspect the DIC/HVAC fuse in the fuse block.

Is the DIC/HVAC fuse open?

--

Go to Step 2

Go to Step 3

2

Locate and repair a short to ground in circuit 541 (BRN).

Is the repair complete?

--

Go to Step 13

--

3

  1. Turn the ignition switch to the on position.
  2. Connect a test lamp between the vacuum/electric solenoid harness connector terminal 6 and ground.

Does the test lamp light?

--

Go to Step 5

Go to Step 4

4

Locate and repair a poor connection or an open in circuit 541 (BRN). Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 13

--

5

  1. Place the heater A/C control in the Defrost mode.
  2. Connect a test lamp between B+ and circuit 366 (LT GRN/BLK) at the vacuum/electric solenoid harness connector terminal 1.

Does the test lamp light?

--

Go to Step 8

Go to Step 6

6

Check for poor connection or open in circuit 366 (LT GRN/BLK). Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems.

Is there a poor connection or open in the circuit?

--

Go to Step 7

Go to Step 11

7

Locate and repair the fault in circuit 366 (LT GRN/BLK). Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 13

--

8

  1. Keep the mode selector in the DEFR position.
  2. Connect a test lamp between B+ and circuit 362 (RED) at the vacuum/electric solenoid connector terminal 2.

Does the test lamp light?

--

Go to Step 9

Go to Step 12

9

Use a DMM in order to test for a short to ground between the heater A/C control harness connector terminal D10 and the vacuum/electric solenoid harness connector, terminal 2.

Is there a short to ground?

--

Go to Step 10

Go to Step 11

10

Locate and repair the short to ground in circuit 362 (RED). Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 13

--

11

Replace the heater-A/C control. Refer to Control Assembly Replacement .

Is the repair complete?

--

Go to Step 13

--

12

Replace the vacuum/electric solenoid. Refer to Vacuum Electrical Solenoid Replacement .

Is the repair complete?

--

Go to Step 13

--

13

Verify that the system operates properly.

Does the system operate properly ?

--

System OK

GO to Diagnostic System Check