GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 GMC C Sierra - 2WD 🢒 Body 🢒 Wiring Systems 🢒 Blower Motor Always On

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step checks for continuous operation of the blower motor.

    2.

  2. The test lamp should not illuminate while connected to any of the blower motor control circuits when the blower motor switch is in the OFF position. Illumination of the test lamp during this step indicates a malfunctioning blower motor switch or a short to voltage on a blower motor control circuit.

    3.

  3. Test the blower motor control circuit that illuminated the test lamp in Step 3.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

DEFINITION: The blower motor is ON while the blower motor switch is in the OFF 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. Place the blower motor switch in the OFF position.

Is the blower motor OFF?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Important: The blower motor switch must remain in the OFF position during this step.

  1. Turn OFF the ignition.
  2. Disconnect the blower motor resistor assembly connector.
  3. Turn On the ignition, with the engine OFF.
  4. Probe each blower motor control circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate while connected to any of the blower motor control circuits?

Go to Step 4

Go to Step 5

4

Test the appropriate blower motor control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 7

5

Visually inspect the blower motor supply voltage circuit of the blower motor harness for a short to voltage with the vehicle harness. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 10

Go to Step 6

6

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

Did you find and correct the condition?

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 .

Did you find and correct the condition?

Go to Step 10

Go to Step 9

8

Replace the blower motor resistor. Refer to Blower Motor Resistor Replacement .

Did you complete the replacement?

Go to Step 10

--

9

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

Did you complete the replacement?

Go to Step 10

--

10

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2