Schematic Reference: HVAC Schematics

DEFINITION: The auxiliary blower motor operates in at least one, but not all, speed positions.

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 in each speed position.

Does the auxiliary 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 auxiliary blower motor connector.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between the auxiliary blower motor supply circuit and the auxiliary blower motor ground circuit.
5. Place the auxiliary blower motor switch in each speed position.

Does the test lamp illuminate and change intensity in each speed position?

Go to Step 7

Go to Step 4

4

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

1. Turn OFF the ignition.
2. Disconnect the auxiliary blower motor resistor assembly connector C1.
3. Probe each auxiliary blower motor speed control circuit with a test lamp that is connected to battery positive voltage.
4. Place the auxiliary blower motor switch in each speed position for the auxiliary blower motor speed control circuit being tested.

Does the test lamp illuminate in each position?

Go to Step 8

Go to Step 5

Test the appropriate auxiliary blower motor speed 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 12

Go to Step 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 12

Go to Step 9

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 12

Go to Step 10

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 12

Go to Step 11

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 12

--

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

Did you complete the replacement?

Go to Step 12

--

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 12

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2

Schematic Reference: HVAC Schematics

DEFINITION: The auxiliary blower motor operates in at least one, but not all, speed positions.

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 switch will only function if the front auxiliary HVAC control switch is placed in the REAR position.

1. Turn ON the ignition, with the engine OFF.
2. Place the auxiliary HVAC control module blower switch in each speed position.

Does the auxiliary blower motor operate in each speed position?

--

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

Go to Step 3

3

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

1. Place the MODE selector in the FLOOR position.
2. Observe the auxiliary blower motor PWM parameter.
3. Rotate the rear HVAC control module blower switch from the min. to max. speed positions.

Does the auxiliary blower motor PWM parameter increase within the specified range?

0-98%

Go to Step 4

Go to Step 5

4

1. Place the front auxiliary HVAC control module blower switch in the min. speed position.
2. Place the MODE selector in the FLOOR position.
3. Observe the auxiliary blower motor PWM parameter.
4. Rotate the front auxiliary HVAC control module blower switch from the min. to max. speed positions.

Does the auxiliary blower motor PWM parameter increase within the specified range?

0-98%

Go to Step 7

Go to Step 6

Test the 5 volt reference and low reference circuits between the front and rear HVAC control modules for an open, a short to voltage, short to ground or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 10

Test the blower speed control circuit between the front and rear HVAC control switches for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 8

Test the rear blower motor control module control circuit for a short to voltage, high resistance. 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

1. Disconnect the auxiliary blower motor connector.
2. Connect a test lamp between the auxiliary blower motor supply circuit and ground circuit.
3. Rotate the fan control switch from the min. to max. speed position.

Does the test lamp illuminate and change intensity?

--

Go to Step 15

Go to Step 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 12

Inspect for poor connections at the harness connector of the front 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

Inspect for poor connections at the harness connector of the rear 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 14

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

Did you complete the replacement?

--

Go to Step 16

--

Replace the front HVAC control module. Refer to Auxiliary Heater and Air Conditioning Control Replacement - Front in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

--

Go to Step 16

--

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

Did you complete the replacement?

--

Go to Step 16

--

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

did you complete the replacement?

--

Go to Step 16

--

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2