GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Sierra - 2WD 🢒 HVAC 🢒 HVAC - Manual 🢒 Blower Motor Malfunction

Test Description

  1. This step verifies that the HVAC control module Fan Up Switch parameter matches the requested state of the blower motor switch.

    2.

  2. This step verifies that the HVAC control module Fan Down Switch parameter matches the requested state of the blower motor switch.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

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

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the Fan Up Button parameter in the Heating and Air Conditioning data list.
  3. Activate the fan up switch.

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

--

Go to Step 3

Go to Step 10

3

  1. With a scan tool, observe the Fan Down Button parameter in the Heating and Air Conditioning data list.
  2. Activate the fan down switch.

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

--

Go to Step 4

Go to Step 10

4

Place the blower motor switch in each speed position.

Does the blower motor operate at the desired speeds?

--

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 5

5
  1. Disconnect the harness connector of the blower motor control processor.
  2. Measure the voltage between the battery positive voltage circuit and the ground circuit of the blower motor control processor.

Does the voltage measure within the specified range?

10-14 V

Go to Step 6

Go to Step 8

6
  1. Connect the blower motor control processor.
  2. Disconnect the harness connector of the HVAC control module.
  3. Measure the voltage on the blower motor speed control circuit.

Does the voltage measure within the specified range?

4.5-5.5 V

Go to Step 9

Go to Step 7

7

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

Did you find and correct the condition?

--

Go to Step 14

Go to Step 9

8

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

Did you find and correct the condition?

--

Go to Step 14

Go to Step 11

9

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 .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

10

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 14

Go to Step 13

11

Repair a high resistance in the ground circuit of the blower motor control processor. Refer to Circuit Testing .

Did you complete the repair?

--

Go to Step 14

--

12

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

Did you complete the replacement?

--

Go to Step 14

--

13

Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 14

--

14

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2