GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C Sierra - 2WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Blower Motor Malfunction

Test Description

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

  1. This step will determine if one or more of the blower speeds is inoperative.

    2.

  2. This step determines if there is battery positive voltage at the blower motor resistor assembly.

    3.

  3. This step tests for voltage in each blower motor control circuit.

    4.

  4. This step tests for an open in the blower motor resistor assembly.

Step

Action

Yes

No

Schematic Reference : HVAC Schematics

DEFINITION: The blower motor operates in at least one speed position, but not in all speed positions.

1

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

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

2

  1. Turn ON the ignition, with the engine OFF.
  2. Position the mode selector to the vent position.
  3. Place the blower motor switch in each speed position.

Does the blower motor operate in each speed position?

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

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the connector C1 at the blower motor resistor assembly .
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery positive voltage circuit of the blower motor resistor assembly with a test lamp that is connected to ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 6

4

Important: Place the blower motor switch in the correct speed position for the control circuit being tested.

  1. Turn OFF the ignition.
  2. Disconnect the connector C1 at the blower motor resistor assembly .
  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 known good ground.
  5. Place the blower motor switch in the appropriate speed position for the control circuit being tested.

Does the test lamp illuminate in each speed position?

Go to Step 5

Go to Step 7

5

  1. Turn OFF the ignition.
  2. Connect connector C1 of the blower motor resistor assembly .
  3. Disconnect the blower motor.
  4. Turn ON the ignition, with the engine OFF.
  5. Probe the voltage circuit of the blower motor with a test lamp that is connected to ground.
  6. Place the blower motor switch in each speed position.

Does the test lamp illuminate in each speed position?

Go to Step 8

Go to Step 9

6

Repair the battery positive voltage circuit to the blower motor resistor assembly for an open or for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

--

7

Test the appropriate blower motor control circuit for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

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

Did you complete the replacement?

Go to Step 11

--

9

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

Did you complete the replacement?

Go to Step 11

--

10

Replace the HVAC control module. Refer to Heater and Air Conditioning Control Replacement .

Did you complete the replacement?

Go to Step 11

--

11

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2