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 - Manual

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

Does the blower motor operate at the correct speed in each speed position?

Go to Step 3

Go to Step 4

1. Place the blower motor switch in the maximum speed position.
2. Place the mode control in each mode position.

Does the blower motor operate in each mode position?

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

Go to Step 18

1. Turn OFF the ignition.
2. Disconnect the blower motor.
3. Turn ON the ignition, with the engine OFF.
4. Connect a test lamp between the blower motor supply voltage circuit of the blower motor and a good ground.
5. Place the blower motor switch in each speed position.

Does the test lamp illuminate in each speed position?

Go to Step 16

Go to Step 5

Does the test lamp illuminate in the maximum speed position?

Go to Step 10

Go to Step 6

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

Does the test lamp illuminate?

Go to Step 7

Go to Step 19

1. Place the blower motor switch in the maximum speed position.
2. Probe the high blower motor control circuit of the blower motor relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 8

Test the high blower motor control circuit of the blower motor 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 24

Go to Step 14

Test the ground circuit of the blower motor 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 24

Go to Step 15

1. Turn OFF the ignition.
2. Disconnect the blower motor relay.
3. Turn ON the ignition, with the engine OFF.
4. Probe the blower motor supply voltage circuit (from the blower motor resistor) with a test lamp that is connected to a good ground.
5. Place the blower motor switch in the minimum, medium 1, and medium 2 speed positions.

Does the test lamp illuminate in each speed position?

Go to Step 15

Go to Step 11

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

Did you find and correct the condition?

Go to Step 24

Go to Step 12

1. Turn OFF the ignition.
2. Disconnect the blower motor resistor.
3. Turn ON the ignition, with the engine OFF.
4. Place the mode control in the vent position.
5. Probe the low, medium 1, and medium 2 blower motor control circuits with a test lamp that is connected to good ground.
6. Place the blower motor switch in the appropriate speed position for the circuit being tested.

Does the test lamp illuminate in each speed position?

Go to Step 17

Go to Step 13

Test the suspect blower motor control circuit of the blower motor resistor 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 24

Go to Step 18

Test the OFF 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 24

Go to Step 18

Inspect for poor connections at the harness connector of the blower motor 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 24

Go to Step 20

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 24

Go to Step 21

Inspect for poor connections at the harness connector of the blower motor resistor. 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 24

Go to Step 22

Inspect for poor connections at the harness connector of the 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 24

Go to Step 23

Repair the battery positive voltage circuit of the blower motor relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 24

--

Replace the blower motor relay.

Did you complete the replacement?

Go to Step 24

--

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

Did you complete the replacement?

Go to Step 24

--

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 24

--

Replace the HVAC control assembly. Refer to Heater and Air Conditioning Control Replacement .

Did you complete the replacement?

Go to Step 24

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3