GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Yukon - 2WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Blower Motor Inoperative at Any Speed

Blower Motor Inoperative at Any Speed Front

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 any speed setting.

    2.

  2. This step tests for voltage at the blower motor.

    3.

  3. This step tests for a possible open in the blower motor ground circuit.

    4.

  4. This step tests for output voltage from the blower motor switch.

Step

Action

Yes

No

Schematic Reference: HVAC Blower Control Schematics

1

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

Go to Step 2

Go to Symptoms

2

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

Is the blower motor inoperative in each speed position?

Go to Step 3

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

3

  1. Turn OFF the ignition.
  2. Disconnect the blower motor.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the blower motor supply circuit and a good ground.
  5. Place the blower motor switch in the minimum speed position.

Does the test lamp illuminate?

Go to Step 4

Go to Step 5

4

  1. Connect a test lamp between the blower motor supply circuit and the blower motor ground circuit.
  2. Place the blower motor switch in the minimum speed position.

Does the test lamp illuminate?

Go to Step 9

Go to Step 8

5

Important: The blower motor switch must be in the correct speed position for the blower motor control circuit being tested. Failure to do this will result in a misdiagnosis.

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

Does the test lamp illuminate?

Go to Step 10

Go to Step 6

6

Test the HVAC module ignition 3 voltage circuit for an open, high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 7

7

Test each blower motor 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 15

Go to Step 11

8

Test the ground circuit of the blower motor resistor assembly for an open or high resistance.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 10

9

Inspect for poor connections at the harness connector of the blower motor. 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 15

Go to Step 13

10

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 14

11

Inspect for poor connections at the harness connectors of the HVAC 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 15

Go to Step 12

12

Replace HVAC module. Refer to Control Assembly Replacement .

Did you complete the replacement?

Go to Step 15

--

13

Replace blower motor. Refer to Blower Motor and Fan Replacement .

Did you complete the replacement?

Go to Step 15

--

14

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

Did you complete the replacement?

Go to Step 15

--

15

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2

Blower Motor Inoperative at Any Speed Auxiliary

Test Description

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

  1. This step tests for auxiliary blower motor operation in any speed setting.

    2.

  2. This step determines if the malfunction is in the control side of the system.

    3.

  3. Test both the rear auxiliary HVAC control assembly chassis ground circuit and the ground circuit between the front and rear HVAC control assemblies.

Step

Action

Yes

No

Schematic Reference: HVAC Blower Control Schematics

DEFINITION: The auxiliary blower motor is inoperative from both the front and rear auxiliary HVAC control assemblies.

1

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

Go to Step 2

Go to Symptoms

2

  1. Turn ON the ignition, with the engine OFF.
  2. Operate both the front and rear auxiliary blower motor switches in each speed position.

Does the auxiliary blower motor operate in each speed position from both the front and rear blower motor switches?

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 auxiliary blower motor.
  3. Turn ON the ignition, with the engine OFF.
  4. Set the front auxiliary blower motor switch to operate at minimum speed.
  5. Connect a test lamp between the auxiliary blower motor supply circuit and a good ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 6

4

Connect a test lamp between the auxiliary blower motor supply circuit and the auxiliary blower motor ground circuit.

Does the test lamp illuminate?

Go to Step 12

Go to Step 5

5

Test the ground circuit of the auxiliary blower motor resistor assembly for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 13

6
  1. Turn OFF the ignition.
  2. Disconnect the auxiliary blower motor resistor assembly connectors.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the auxiliary blower motor resistor assembly ignition 3 voltage circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 15

7

Probe the auxiliary blower motor resistor assembly battery positive voltage circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 8

Go to Step 16

8

  1. Set the front auxiliary blower motor switch to operate at minimum speed.
  2. Probe the auxiliary blower motor low speed control circuit with a test lamp that is connected to battery positive voltage.

Does the test lamp illuminate?

Go to Step 13

Go to Step 9

9
  1. Turn OFF the ignition.
  2. Disconnect the front auxiliary HVAC control assembly
  3. Probe the front auxiliary HVAC control assembly ground circuit with a test lamp that is connected to battery positive voltage.

Does the test lamp illuminate?

Go to Step 14

Go to Step 10

10

Test the auxiliary HVAC control assembly ground circuits for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 11

11

Inspect for poor connections at the harness connector of the rear auxiliary HVAC control assembly. 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 21

Go to Step 17

12

Inspect for poor connections at the harness connector of the auxiliary blower motor. 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 21

Go to Step 19

13

Inspect for poor connections at the harness connectors of the auxiliary blower motor resistor assembly. 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 21

Go to Step 20

14

Inspect for poor connections at the harness connector of the front auxiliary HVAC control assembly. 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 21

Go to Step 18

15

Repair the ignition 3 voltage circuit of the auxiliary blower motor resistor assembly. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 21

--

16

Repair the battery positive voltage circuit of the auxiliary blower motor resistor assembly. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 21

--

17

Replace rear auxiliary HVAC control assembly. Refer to Control Assembly Replacement - Auxiliary .

Did you complete the replacement?

Go to Step 21

--

18

Replace front auxiliary HVAC control assembly. Refer to Control Assembly Replacement - Auxiliary .

Did you complete the replacement?

Go to Step 21

--

19

Replace auxiliary blower motor. Refer to Auxiliary Blower Motor Replacement .

Did you complete the replacement?

Go to Step 21

--

20

Replace auxiliary blower motor resistor assembly. Refer to Auxiliary Blower Motor Resistor Replacement .

Did you complete the replacement?

Go to Step 21

--

21

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2