Schematic Reference: HVAC Schematics

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

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

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

1. Turn ON the ignition, with the engine OFF.
2. Place the mode switch in any position except OFF.
3. 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

Does the blower motor operate in the medium speed position?

Go to Step 4

Go to Step 5

Does the blower motor operate in the maximum speed position?

Go to Step 17

Go to Step 12

1. Turn OFF the ignition.
2. Disconnect the blower motor 1 relay.
3. Turn ON the ignition with the engine OFF.
4. Connect a 30-amp fused jumper wire between the battery positive voltage circuit and blower motor resistor supply voltage circuit of blower motor 1 relay.

Does the blower motor operate in medium speed?

Go to Step 9

Go to Step 6

Test blower motor resistor supply voltage circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 7

Test the medium blower motor supply voltage circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 8

1. Turn OFF the ignition.
2. Disconnect the blower motor 2 relay.
3. Turn ON the ignition with the engine OFF.
4. Connect a test lamp between ground and the medium blower motor supply voltage circuit of the blower motor 2 relay.

Does the test lamp illuminate?

Go to Step 24

Go to Step 25

1. Place the blower control in the medium position.
2. Connect a test lamp between the ignition 3 voltage circuit and the medium blower motor control circuit of the blower motor 1 relay.

Does the test lamp illuminate?

Go to Step 23

Go to Step 10

Test the ignition 3 voltage circuit of blower motor 1 relay for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 11

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

Did you find and correct the condition?

Go to Step 34

Go to Step  26

1. Turn OFF the ignition.
2. Disconnect the blower motor 2 relay.
3. Turn ON the ignition with the engine OFF.
4. Connect a 30-amp fused jumper wire between the blower motor supply voltage circuit and the blower motor relay supply voltage circuit of blower motor 2 relay.

Does the blower motor operate at high speed?

Go to Step 14

Go to Step 13

Test the blower motor relay supply voltage circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 23

1. Place the blower control in the maximum speed position.
2. Connect a test lamp between the ignition 3 voltage circuit and the high blower motor control circuit of blower motor 2 relay.

Does the test lamp illuminate?

Go to Step 24

Go to Step 15

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

Did you find and correct the condition?

Go to Step 34

Go to Step 16

Test the ignition 3 voltage circuit of blower motor 2 relay for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 34

Go to Step 26

Backprobe the blower motor supply voltage circuit at the blower motor resistor with a test lamp that is connected to ground. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

Go to Step 28

Go to Step 18

Backprobe the blower motor resistor supply voltage circuit at the blower motor resistor with a test lamp that is connected to ground. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

Go to Step 25

Go to Step 18

1. Turn OFF the ignition.
2. Disconnect the blower motor diode module.
3. Connect a test lamp between the low blower motor control circuit at the blower motor diode module and battery voltage.

Does the test lamp illuminate?

Go to Step 20

Go to Step 22

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

Did you find and correct the condition?

Go to Step 34

Go to Step 21

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

Did you find and correct the condition?

Go to Step 34

Go to Step 27

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

Did you find and correct the condition?

Go to Step 34

Go to Step 26

Inspect for poor connections at the harness connector of the blower motor 1 relay. 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 34

Go to Step 29

Inspect for poor connections at the harness connector of the blower motor 2 relay. 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 34

Go to Step 30

Inspect for poor connections at the harness connector of the 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 34

Go to Step 31

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 34

Go to Step 32

Inspect for poor connections at the harness connector of the blower motor diode 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 34

Go to Step 33

Repair the blower motor supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 34

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Replace the blower motor 1 relay. Refer to Blower Motor Relay Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 34

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Replace the blower motor 2 relay. Refer to Blower Motor Relay Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 34

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

Did you complete the replacement?

Go to Step 34

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

Did you complete the replacement?

Go to Step 34

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Replace the blower motor diode module. Refer to Blower Motor Diode Assembly Replacement in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 34

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Operate the system in order to verify the repair.

Did you correct the condition?

--

Go to Step 2