GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

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

--

Go to Step 2

Go to Symptoms

2

Inspect the HVAC fuse in the fuse block.

Is the HVAC fuse open?

--

Go to Step 3

Go to Step 4

3

Locate and repair a short to ground in circuit 41 (BRN). Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 13

--

4

  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 6

Go to Step 5

5

Locate and repair a poor connection or an open in circuit 41 (BRN). Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 13

--

6

  1. Place the heater A/C control in the Heat mode.
  2. Place the A/C to the OFF position.
  3. Connect a test lamp between B+ and circuit 362 (RED) at the vacuum/electric solenoid harness connector terminal 2.

Does the test lamp light?

--

Go to Step 9

Go to Step 7

7

Inspect for a poor connection or an open in circuit 362 (RED) between he vacuum/electric solenoid harness connector terminal 2 and the heater A/C control module harness connector C2 terminal A5. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems.

Is a poor connection or an open in the circuit?

--

Go to Step 8

Go to Step 11

8

Locate and repair the fault 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

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9

  1. Keep the mode selector in the HEAT position
  2. Connect a test lamp between B+ and circuit 366 (LT GRN/BLK) at the vacuum/electric solenoid connector terminal 1.

Does the test lamp light?

--

Go to Step 10

Go to Step 12

10

Locate and repair the short to ground in circuit 366 (LT GRN/BLK). Refer to Testing for Short to Ground 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

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12

A fault exists in the vacuum/electric solenoid, the vacuum source, the vacuum actuators, the vacuum hoses to actuators, the linkage from actuators to values; or the valves are faulty. Refer to Vacuum System for further diagnosis.

Is the action complete?

--

Go to Step 13

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13

Verify that the system operates properly.

Does the system operate properly?

--

System OK

Go to Symptoms