Schematic Reference: HVAC Blower Control Schematics

DEFINITION: The blower motor is inoperative in all speed positions.

Did you perform the HVAC Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check

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

Does the blower motor operate in any of the speed positions?

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Go to Blower Motor Malfunction

Go to Step 3

1. Place the blower switch in the maximum speed position.
2. With the scan tool observe the Desired Blower Mtr Speed parameter in the Heating and Air Conditioning data list.

Does the scan tool indicate that the Desired Blower Mtr Speed parameter is near the specified value?

111 counts

Go to Step 4

Go to Step 12

1. Turn OFF the ignition.
2. Disconnect the blower motor connector.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between circuit 40 and circuit 754.
5. Place the blower switch in the minimum speed position.

Does the test lamp illuminate?

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Go to Step 10

Go to Step 5

Test the circuit 40 of theblower control module for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 16

Go to Step 6

Test the circuit 150 of the blower control module for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 16

Go to Step 7

Important: Ensure that the blower control module connector and the HVAC control module connectors are connected during this step in order to avoid misdiagnosis.

1. Measure the voltage from circuit 754 at the HVAC control module to a good ground.
2. With a scan tool, command the blower motor OFF and ON.

Does the voltage measure near the specified values for each commanded state?

5.0 V OFF

1.0 V ON

Go to Step 11

Go to Step 8

1. Turn OFF the ignition.
2. Disconnect the HVAC control module.
3. Turn ON the ignition, with the engine OFF.
4. Measure the voltage from the circuit 754 of the HVAC control module to a good ground.

Does the voltage measure near the specified value?

5.0 V

Go to Step 12

Go to Step 9

Test circuit 754 of the HVAC control module for an open, short to ground or 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 11

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?

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Go to Step 16

Go to Step 13

Inspect for poor connections at the harness connector of the blower control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 16

Go to Step 14

Inspect for poor connections at the harness connector 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?

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Go to Step 16

Go to Step 15

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

Did you complete the replacement?

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Go to Step 16

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Replace the blower control module. Refer to Blower Motor Control Module Replacement .

Did you complete the replacement?

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Go to Step 16

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Replace the HVAC control module. Refer to Control Assembly Replacement .

Did you complete the replacement?

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Go to Step 16

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Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2