GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Check 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). Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs In Wiring Systems.

Is the repair complete?

--

Go to Step 10

--

3

  1. Place the ignition switch in 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 10

--

5

  1. Place the mode selector in the Recirculation (MAX) position.
  2. Connect a test lamp between B+ and circuit 363 (TAN) at the vacuum/electric solenoid harness connector terminal 5.

Does the test lamp light?

--

Go to Step 8

Go to Step 6

6

Check for poor connection or open in circuit 363 (TAN).

Is there a poor connection or open in the circuit?

--

Go to Step 7

Go to Step 9

7

Locate and repair the fault in circuit 363 (TAN). Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs In Wiring Systems.

Is the repair complete?

--

Go to Step 10

--

8

A fault exists in one of the following areas. Refer to Vacuum Test for further diagnosis.

    • The vacuum/electric solenoid
    • The vacuum source
    • The vacuum actuators
    • The vacuum hoses to actuators
    • The linkage from actuators to values
    • Faulty valves

Is the action complete?

--

Go to Step 10

--

9

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

Is the repair complete?

--

Go to Step 10

--

10

Verify that the systems operates properly.

Does the system operate properly ?

--

System OK

Go to Diagnostic System Check