GM Service Manual Online
For 1990-2009 cars only

Auxiliary Blower Motor Malfunction Body Type VIN 6

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The auxiliary blower motor operates in at least one speed position from at least one auxiliary control.

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. With a scan tool, observe the Driver Override Switch parameter in the REAR HVAC/RSA data list.
  3. Place the front auxiliary blower motor switch in each position.

Does the scan tool indicate that the Driver Override Switch parameter changes state?

 

Go to Step 6

Go to Step 3

3

Test the Auxiliary HVAC Enable Control circuit of the front auxiliary blower motor switch for an open, short to voltage or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

 

Go to Step 22

Go to Step 4

4

Test the Low Reference circuit of the front auxiliary blower motor switch for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

 

Go to Step 22

Go to Step 5

5

  1. Turn the ignition OFF.
  2. Disconnect the auxiliary HVAC control module.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a volt meter between the Auxiliary HVAC Enable Control circuit and ground.
  5. Place the front auxiliary blower motor switch from the minimum speed position to the maximum speed position.

Does the volt meter read properly for each position?

Rear  5.0V Off-1.0V Pos.1  2.0V Pos.2  3.0V Pos.3  4.0V

Go to Step 16

Go to Step 17

6

Important: Ensure that the front auxiliary blower control switch is in the REAR position during the remainder of this table in order to avoid misdiagnosis.

  1. Turn ON the ignition, with the engine OFF.
  2. Place the front auxiliary blower motor switch in the REAR position.
  3. With a scan tool, observe the Rear Fan Up Button parameter in the REAR HVAC/RSA data list.
  4. Activate the auxiliary fan up switch.

Does the scan tool indicate that the Rear Fan Up Button parameter changes state?

--

Go to Step 7

Go to Step 16

7

  1. With a scan tool, observe the Rear Fan Down Button parameter in the REAR HVAC/RSA data list.
  2. Activate the auxiliary fan down switch.

Does the scan tool indicate that the rear Fan Down Button parameter changes state?

--

Go to Step 8

Go to Step 16

8

Place the auxiliary blower motor switch in each speed position.

Does the auxiliary blower motor operate at the desired speeds?

--

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

Go to Step 9

9

  1. Turn the ignition OFF.
  2. Disconnect the auxiliary blower motor.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the auxiliary blower motor supply voltage circuit and the auxiliary blower motor ground circuit of the auxiliary blower motor.
  5. Place the auxiliary blower motor switch from the minimum speed position to the maximum speed position.

Does the test lamp illuminate and increase intensity?

--

Go to Step 14

Go to Step 10

10

Test the battery positive voltage circuit of the auxiliary blower motor control processor for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 11

11

Test the ground circuit of the auxiliary blower motor control processor for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 12

12

Important: Ensure that the auxiliary blower motor control processor and auxiliary HVAC control module connectors are connected during this step in order to avoid misdiagnosis.

  1. Turn ON the ignition, with the engine OFF.
  2. Measure the voltage from the auxiliary blower motor speed control circuit of the auxiliary HVAC control module to a good ground.
  3. Place the auxiliary blower motor switch from the minimum speed position to the maximum speed position.

Does the voltage continually decrease within the specified range?

13.0-1.5 V

Go to Step 15

Go to Step 13

13

  1. Turn the ignition OFF.
  2. Disconnect the auxiliary HVAC control module.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the auxiliary blower speed control circuit of the auxiliary HVAC control module to a good ground.

Does the voltage measure near the specified value?

8-12.5 V

Go to Step 16

Go to Step 15

14

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

Did you find and correct the condition?

--

Go to Step 22

Go to Step 19

15

Inspect for poor connections at the harness connector of the auxiliary 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?

--

Go to Step 22

Go to Step 20

16

Inspect for poor connections at the harness connector of the auxiliary 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?

--

Go to Step 22

Go to Step 21

17

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

Did you find and correct the condition?

 

Go to Step 22

Go to Step 18

18

Replace the front auxiliary blower motor switch. Refer to Blower Motor Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

 

Go to Step 22

--

19

Replace the auxiliary blower motor. Refer to Blower Motor Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

--

Go to Step 22

--

20

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

Did you complete the replacement?

--

Go to Step 22

--

21

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

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

Did you complete the replacement?

--

Go to Step 22

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22

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2