Schematic Reference: HVAC 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 - HVAC Systems - Automatic

2

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

Does the blower motor operate at the correct speed 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 Commanded Blower parameter in the Heating and Air Conditioning data list.
2. Adjust the blower control from the minimum speed position to the maximum speed position.

Does scan tool indicate that the Commanded Blower parameter increases within the specified range?

0-96%

Go to Step 4

Go to Step 10

4

1. Turn the ignition OFF.
2. Disconnect the blower motor connector.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between the blower motor supply voltage circuit and the blower motor control circuit.
5. Adjust the blower control 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 battery positive voltage circuit and ground circuit of the blower motor control processor 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: The blower motor control processor and HVAC control module connectors must be connected to correctly perform the test.

1. Backprobe and measure the voltage from the blower speed control circuit of the HVAC control module and a good ground.
2. Adjust the blower control from the minimum speed position to the maximum speed position.

Does the measured voltage decrease between the specified values?

4.7-0.65 V

Go to Step 9

Go to Step 7

1. Turn the ignition OFF.
2. Disconnect the HVAC control module.
3. Turn ON the ignition, with the engine OFF.
4. Measure the voltage from the blower speed control circuit 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 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 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 Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

--

Go to Step 14

--

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

Did you complete the replacement?

--

Go to Step 14

--

Important: Perform the recalibration procedure for the HVAC control module.

Replace the HVAC control module. Refer to HVAC Control Module 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