GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The blower motor is ON while the HVAC control is in the OFF position.

1

Did you perform the HVAC Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

  1. Turn ON the ignition, with the engine OFF.
  2. Turn OFF the HVAC controls.

Is the blower motor OFF?

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

Go to Step 3

3

  1. Install a scan tool.
  2. With the scan tool, observe the Desired Blower Mtr Speed parameter in the Heating and Air Conditioning data list.

Does the scan tool indicate that the Desired Blower Mtr Speed parameter is near the specified value?

0  counts

Go to Step 4

Go to Step 7

4

Disconnect the HVAC control module.

Does the blower motor continue to operate?

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Go to Step 5

Go to Step 7

5

Inspect or test the blower motor housing and the blower motor speed control circuit in the blower motor harness for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 10

Go to Step 6

6

Inspect for poor connections at the harness connector of the blower motor control processor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 10

Go to Step 8

7

Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 10

Go to Step 9

8

Replace the blower motor control processor. Refer to Blower Motor Control Processor Replacement .

Did you complete the replacement?

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Go to Step 10

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9

Replace the HVAC control module. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

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Go to Step 10

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10

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 3