GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Avalanche - 4WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Auxiliary Blower Motor Always On

Test Description

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

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

    2.

  2. The Blower Motor Test parameter must be commanded ON before an OFF command will function.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

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

1

Did you perform the HVAC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic in Wiring Systems

2

  1. Turn ON the ignition, with the engine OFF.
  2. Place the auxiliary blower motor switch on the front HVAC control assembly in the OFF position.

Does the auxiliary blower motor operate?

--

Go to Step 3

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

3
  1. With a scan tool, command the Blower Motor Test parameter ON. in the Rear Aux. Climate Module Scan Tool Output Controls.
  2. Command the Blower Motor Test parameter OFF.
  3. Observe the Blower Motor PWM parameter in the Rear Aux Climate Module Scan Tool Data List.

Does the scan tool indicate that the Blower Motor PWM parameter is at 0 %?

--

Go to Step 4

Go to Step 14

4
  1. Place the front auxiliary blower motor switch in the medium speed position.
  2. Place the front auxiliary air temperature switch to the 74°F position.
  3. Place the front auxiliary mode switch in the bi-level position.
  4. With a scan tool, observe the following parameters in the Rear Aux. Climate Module Front Aux. Controls data list:
    5. • Air Temp. Switch Pos.
    • Blower Switch Pos.
    • Mode Switch Pos.

Does the scan tool indicate that each parameter is 0?

--

Go to Step 7

Go to Step 5

5

With a scan tool, observe the following parameters in the Rear Aux. Climate Module Front Aux. Controls data list:

    • Air Temp. Switch Pos.
    • Blower Switch Pos.
    • Mode Switch Pos.

Does the scan tool indicate that each parameter is above 13?

--

Go to Step 9

Go to Step 6

6
  1. Place the auxiliary blower motor switch on the front auxiliary HVAC control assembly in the maximum speed position.
  2. With a scan tool, observe the Blower Switch Pos. parameter.

Does the scan tool indicate that Blower Switch Pos. parameter is 15?

--

Go to Step 13

Go to Step 11

7
  1. Disconnect the front auxiliary HVAC control assembly.
  2. Measure the voltage from the 5 volt reference circuit of the front auxiliary HVAC control assembly to a good ground.

Does the voltage measure greater than the specified value?

4.5 V

Go to Step 14

Go to Step 8

8

Test the 5 volt reference circuit of the front auxiliary HVAC control assembly for a short to ground, short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 14

9
  1. Disconnect the front auxiliary HVAC control assembly.
  2. Measure the voltage from the low reference circuit of the front auxiliary HVAC control assembly to the battery positive voltage.

Does the voltage measure greater than the specified value?

11.5 V

Go to Step 14

Go to Step 10

10

Test the low reference circuit of the front auxiliary HVAC control assembly for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 14

11

Test the auxiliary front blower motor speed signal circuit of the front auxiliary HVAC control assembly for a short to voltage, a short to ground, a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 12

12
  1. Connect the front auxiliary HVAC control assembly.
  2. Measure the voltage on the auxiliary front blower motor speed signal circuit.
  3. Place the auxiliary blower motor switch on the front HVAC control assembly from the minimum speed position to the maximum speed position.

Does the voltage increase as the auxiliary blower motor switch is rotated to maximum speed?

--

Go to Step 14

Go to Step 15

13

Inspect for poor connections at the harness connector of the auxiliary blower motor 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 19

Go to Step 16

14

Inspect for poor connections at the harness connector of the auxiliary 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 19

Go to Step 17

15

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 19

Go to Step 18

16

Replace the auxiliary blower motor control processor. Refer to Auxiliary Blower Motor Processor Replacement .

Did you complete the replacement?

--

Go to Step 19

--

17

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

Did you complete the replacement?

--

Go to Step 19

--

18

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

Did you complete the replacement?

--

Go to Step 19

--

19

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2