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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Avalanche - 4WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Auxiliary Blower Motor Always On

Auxiliary Blower Motor Always On W/Sunroof or Heat Only

Test Description

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

  1. This step checks for continuous operation of the auxiliary blower motor.

    2.

  2. This step determines if the malfunction is in the auxiliary HVAC control assembly.

    3.

  3. This step tests for a short to ground in the control side of the system. It is easiest to perform this step by disconnecting the auxiliary blower motor resistor assembly connector C1 and the auxiliary HVAC control assembly. Test each auxiliary blower motor speed control circuit for continuity to a known good ground.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: The auxiliary blower motor is on while the auxiliary blower motor switch is in the OFF position.

1

Did you review the auxiliary 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 auxiliary blower motor switch to the OFF position.

Is the blower motor OFF?

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 HVAC control assembly.
  3. Turn ON the ignition, with the engine OFF.

Is the blower motor OFF?

Go to Step 6

Go to Step 4

4

Test each auxiliary blower motor speed control circuit between the auxiliary blower motor resistor assembly and the auxiliary HVAC control assembly 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 9

Go to Step 5

5

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 9

Go to Step 8

6

Inspect for poor connections at the harness connector of the 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 9

Go to Step 7

7

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

Did you complete the replacement?

Go to Step 9

--

8

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

Did you complete the replacement?

Go to Step 9

--

9

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2

Auxiliary Blower Motor Always On W/O Sunroof

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 the OFF setting.

    2.

  2. This step tests for a possible short to ground in the auxiliary blower motor control module control circuit.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

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

1

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

--

Go to Step 2

Go to Symptoms - HVAC Systems - Automatic

2

Important: The rear auxiliary HVAC control module will only function if the front auxiliary HVAC control module is placed in the REAR position.

  1. Turn ON the ignition, with the engine OFF.
  2. Place both of the auxiliary HVAC control modules in the OFF position.

Does the auxiliary blower motor operate in the OFF position?

--

Go to Step 3

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

3

Important: Place the front auxiliary HVAC control module in the REAR position. Place the rear auxiliary HVAC control module in the OFF position. Place the MODE selector in any position except AUTO. Failure to do this may result in a misdiagnosis.

  1. Place the rear auxiliary HVAC control module in the OFF position
  2. Place the MODE selector in the FLOOR position.
  3. Command the auxiliary blower motor to the OFF state.
  4. Observe the auxiliary blower motor PWM parameter.

Is the auxiliary blower motor PWM parameter at the specified value?

0%

Go to Step 4

Go to Step 11

4

Disconnect the rear auxiliary HVAC control module.

Is the blower motor operating?

--

Go to Step 6

Go to Step 5

5
  1. Connect the rear auxiliary HVAC control module connector.
  2. Place the rear auxiliary HVAC control module in the OFF position.
  3. Disconnect the front auxiliary HVAC control module connector.

Is the blower motor operating at the specified value?

14%

Go to Step 10

Go to Step 8

6

Test the rear auxiliary blower motor control module 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 7

7

Test the blower motor supply circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 12

8

Test the low reference circuit between the front auxiliary control module and the rear auxiliary control module for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 9

9

Test the 5 volt reference circuit between the front auxiliary control module and the rear auxiliary control module for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 11

10

Inspect for poor connections at the harness connector of the front 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 16

Go to Step 13

11

Inspect for poor connections at the harness connector of the rear 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 16

Go to Step 14

12

Inspect for poor connections at the harness connector of the auxiliary blower motor 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 16

Go to Step 15

13

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

Did you complete the replacement?

--

Go to Step 16

--

14

Replace the rear HVAC control module. Refer to Auxiliary Heater and Air Conditioning Control Replacement - Front .

Did you complete the replacement?

--

Go to Step 16

--

15

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

Did you complete the replacement?

--

Go to Step 16

--

16

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2