GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Yukon Denali 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Blower Motor Malfunction

Test Description

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

  1. This step will determine if one or more blower speeds are 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, but not 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 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 blower motor resistor assembly connector C1.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the battery positive voltage circuit of the blower motor resistor assembly and a good ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 6

4

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

  1. Turn OFF the ignition.
  2. Disconnect the blower motor resistor assembly connector C1.
  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 blower motor 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 the blower motor resistor assembly connector C1.
  3. Disconnect the blower motor.
  4. Turn ON the ignition, with the engine OFF.
  5. Probe the blower motor voltage circuit of the blower motor with a test lamp that is connected to a good 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 short to ground. Refer to Circuit Testing and 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 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