GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The blower motor operates with the HVAC controls 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

Important: Be sure that the blower motor housing is not shorted to a grounded surface this will cause the blower motor to always be on in high speed.

  1. Turn the ignition ON, 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

With the scan tool observe the Blower Motor PWM Speed parameter in the Heating and Air Conditioning data list.

Does the scan tool indicate that the Blower Motor PWM Speed parameter is near the specified value?

0%

Go to Step 4

Go to Step 6

4

  1. Turn the ignition OFF.
  2. Disconnect the HVAC control module.
  3. Turn ON the ignition, with the engine OFF.

Is the blower motor OFF?

--

Go to Step 6

Go to Step 5

5

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

Did you find and correct the condition?

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Go to Step 9

Go to Step 7

6

Inspect for poor connections at the harness connector of the HVAC control module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 8

7

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

Did you complete the replacement?

--

Go to Step 9

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8

Important: Perform the recalibration procedure for the HVAC control module.

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

Did you complete the replacement?

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Go to Step 9

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9

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2