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 is inoperative in all speed positions.

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn ON the ignition, with the engine OFF.
  2. Place the blower switch in each speed position.

Does the blower motor operate in any speed position?

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Go to Blower Motor Malfunction

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the blower motor connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the blower motor supply voltage circuit and the blower motor control circuit.
  5. Place the blower switch in the maximum speed position.

Does the test lamp illuminate?

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Go to Step 10

Go to Step 4

4

Test the battery positive voltage circuit of the blower motor control processor for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

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Go to Step 16

Go to Step 5

5

Test the ground circuit of the blower motor control module for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 6

6

Important: The blower motor control module connector and the HVAC control module connectors must be connected to correctly perform the test.

  1. Backprobe and measure the voltage from the blower speed control circuit at the HVAC control module to a good ground.
  2. With a scan tool, command the blower motor ON and OFF.

Does the voltage measure near the specified values for each commanded state?

2.0 V OFF

8.0 V ON

Go to Step 7

Go to Step 9

7

Test the blower motor voltage supply circuit between the blower motor and the blower motor control module for an open, short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

 

Go to Step 16

Go to Step 8

8

Test the blower speed control circuit between the blower motor and the blower motor control module for an open, short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

 

Go to Step 16

Go to Step 11

9

Test the blower speed control circuit of the HVAC control module for an open, short to ground or short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

 

Go to Step 16

Go to Step 12

10

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

Did you find and correct the condition?

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Go to Step 16

Go to Step 13

11

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

Did you find and correct the condition?

--

Go to Step 16

Go to Step 14

12

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 .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 15

13

Replace the blower motor. Refer to Blower Motor Replacement .

Did you complete the replacement?

--

Go to Step 16

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14

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

Did you complete the replacement?

--

Go to Step 16

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15

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

Did you complete the replacement?

--

Go to Step 16

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16

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2