GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C Sierra - 2WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Blower Motor Always On

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step tests for blower motor operation in the OFF setting.

    2.

  2. This step tests for a possible short to ground on the blower motor control circuit.

    3.

  3. This step tests for a possible short to voltage in the blower motor supply circuit.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: The blower motor is ON while the HVAC controls are in the OFF position.

1

Did you review the HVAC operation and perform the necessary inspections?

--

Go to Step 2

Go to Symptoms - HVAC Systems - Automatic

2

  1. Turn ON the ignition, with the engine OFF.
  2. Place the HVAC control module in the OFF position.

Does the blower motor operate in the OFF position?

--

Go to Step 3

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

3

Important: Place the MODE selector in any position except AUTO. Failure to do this may result in a misdiagnosis.

  1. Place the HVAC control switch in the OFF position
  2. Place the MODE selector in the FLOOR position.
  3. Command the blower motor to the OFF state.
  4. Observe the blower motor PWM parameter.

Is the blower motor PWM parameter at the specified value?

0%

Go to Step 4

Go to Step 7

4

Test the Heater and A/C blower motor control module blower speed control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 5

5

Test the blower motor supply circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 6

6

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 in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 8

7

Replace the HVAC control module. Refer to HVAC Control Module Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

--

Go to Step 9

--

8

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

Did you complete the replacement?

--

Go to Step 9

--

9

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2