Schematic Reference: HVAC Blower Control Schematics

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

Did you perform the HVAC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

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

Does the blower motor operate in each speed position?

--

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

Go to Step 3

1. With a scan tool, observe the Desired Blower Mtr Speed parameter in the Heating and Air Conditioning data list.
2. Gradually adjust the blower motor switch from the minimum speed position to the maximum speed position.

Does scan tool indicate that the Desired Blower Mtr Speed parameter continuously increases within the specified range?

15-111 counts

Go to Step 4

Go to Step 10

4

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 the circuit 754.
5. Place the blower motor switch from the minimum speed position to the maximum speed position.

Does the test lamp illuminate and increase intensity?

--

Go to Step 8

Go to Step 5

Test the circuit 40 and circuit 150 of the blower control module for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 6

6

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

1. Measure the voltage from the circuit 754 at the HVAC control module to a good ground.
2. Place the blower motor switch from the minimum speed position to the maximum speed position.

Does the measured voltage continuously decrease between the specified values?

4.7-1.0 V

Go to Step 9

Go to Step 7

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 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 10

Go to Step 9

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?

--

Go to Step 14

Go to Step 11

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?

--

Go to Step 14

Go to Step 12

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?

--

Go to Step 14

Go to Step 13

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

Did you complete the replacement?

--

Go to Step 14

--

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

Did you complete the replacement?

--

Go to Step 14

--

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

Did you complete the replacement?

--

Go to Step 14

--

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2