GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Express 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Auxiliary Blower Motor Malfunction

Test Description

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

  1. Test the circuit that did not illuminate the test lamp in Step 6.

    2.

  2. The control circuit of the auxiliary blower motor relay is the circuit which provides the ground path for the relay coil through the auxiliary blower motor switch(es).

    3.

  3. Test the blower motor control circuit that corresponds with the inoperative blower motor speed.

    4.

  4. The auxiliary blower motor switch control circuit is the circuit that enables the rear auxiliary HVAC control assembly when the front auxiliary blower motor switch is placed in the rear control position.

    5.

  5. The auxiliary blower motor switch control circuit is the circuit that enables the rear auxiliary HVAC control assembly when the front auxiliary blower motor switch is placed in the rear control position.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: The auxiliary 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. Place the front auxiliary blower motor switch in each speed position.

Does the auxiliary blower motor operate properly in each speed position?

Go to Step 3

Go to Step 5

3

Is the vehicle equipped with both front and rear auxiliary HVAC control assemblies?

Go to Step 4

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

4
  1. Place the front auxiliary blower motor switch in the rear control position.
  2. Place the rear auxiliary blower motor switch in each speed position.

Does the auxiliary blower motor operate properly in each speed position?

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

Go to Step 13

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

Does the test lamp illuminate in each speed position?

Go to Step 12

Go to Step 6

6
  1. Turn OFF the ignition.
  2. Disconnect the auxiliary blower motor resistor assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe each circuit of the auxiliary blower motor resistor assembly with a test lamp that is connected to a good ground.
  5. Place the front auxiliary blower motor switch in the appropriate speed position for the circuit being tested.

Does the test lamp illuminate on each circuit?

Go to Step 20

Go to Step 7

7

Test the applicable circuit between the auxiliary blower motor resistor assembly and the corresponding auxiliary blower motor relay 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 33

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Disconnect the applicable auxiliary blower motor relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ignition 3 voltage circuit of the auxiliary blower motor relay and a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 25

9

Connect a test lamp between the battery positive voltage circuit of the auxiliary blower motor relay and a good ground.

Does the test lamp illuminate?

Go to Step 10

Go to Step 26

10

  1. Connect a test lamp between the battery positive voltage circuit and the control circuit of the auxiliary blower motor relay.
  2. Place the front auxiliary blower motor switch in the appropriate position for the circuit being tested.

Does the test lamp illuminate?

Go to Step 19

Go to Step 11

11

Test the applicable control circuit of the auxiliary blower motor relay between the relay and the front auxiliary HVAC control 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 33

Go to Step 22

12

Test the ground circuit of the auxiliary blower motor for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 33

Go to Step 21

13

Does the auxiliary blower motor operate in any rear auxiliary blower motor switch speed position?

Go to Step 14

Go to Step 15

14

Test the applicable blower motor control circuit of the rear auxiliary HVAC control assembly between the rear auxiliary HVAC control assembly and the splice 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 33

Go to Step 23

15

  1. Turn OFF the ignition.
  2. Disconnect the front auxiliary HVAC control assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. Place the rear auxiliary blower motor switch in the maximum speed position.
  5. Connect a 3 amp fused jumper wire between the auxiliary blower motor switch control circuit of the front auxiliary HVAC control assembly and ground.

Does the auxiliary blower motor operate?

Go to Step 22

Go to Step 16

16

  1. Turn OFF the ignition.
  2. Disconnect the auxiliary HVAC control processor.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a 3 amp fused jumper wire between the auxiliary blower motor switch control circuit of the auxiliary HVAC control processor and ground.

Does the auxiliary blower motor operate?

Go to Step 17

Go to Step 18

17

Test the auxiliary blower motor switch control circuit between the front auxiliary HVAC control assembly and the auxiliary HVAC control processor 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 33

Go to Step 24

18

Test the auxiliary blower motor switch control circuit between the rear auxiliary HVAC control assembly and the auxiliary HVAC control processor 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 33

Go to Step 23

19

Inspect for poor connections at the harness connector of the applicable auxiliary blower motor relay. 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 33

Go to Step 27

20

Inspect for poor connections at the harness connector 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 33

Go to Step 28

21

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 33

Go to Step 29

22

Inspect for poor connections at the harness connector of the auxiliary blower motor switch (w/o rear A/C) or the front auxiliary HVAC control assembly (w/ rear A/C). 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 33

Go to Step 30

23

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 33

Go to Step 31

24

Inspect for poor connections at the harness connector of the auxiliary HVAC control processor. 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 33

Go to Step 32

25

Repair the ignition 3 voltage circuit between the splice and the relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 33

--

26

Repair the battery positive voltage circuit between the splice and the relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 33

--

27

Replace the appropriate auxiliary blower motor relay. Refer to Auxiliary Blower Motor Relay Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 33

--

28

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

Did you complete the replacement?

Go to Step 33

--

29

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

Did you complete the replacement?

Go to Step 33

--

30

Replace the auxiliary blower motor switch (w/o rear A/C) or the front auxiliary HVAC control assembly (w/ rear A/C). Refer to Auxiliary Blower Motor Switch Replacement or Auxiliary Heater and Air Conditioning Control Replacement - Front .

Did you complete the repair?

Go to Step 33

--

31

Replace the rear auxiliary HVAC control assembly. Refer to Auxiliary Heater and Air Conditioning Control Replacement - Rear .

Did you complete the repair?

Go to Step 33

--

32

Replace the auxiliary HVAC control processor. Refer to Auxiliary HVAC Control Processor Replacement .

Did you complete the repair?

Go to Step 33

--

33

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2