GM Service Manual Online
For 1990-2009 cars only

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Schematic Reference: HVAC Schematics

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

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

2

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

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

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

Go to Step 3

3

  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 the minimum speed position.

Does the test lamp illuminate?

Go to Step 4

Go to Step 5

4

Test the ground circuit of the blower motor 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 16

Go to Step 10

5

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

Does the test lamp illuminate?

Go to Step 8

Go to Step 6

6

Test the low 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 16

Go to Step 7

7

  1. Turn OFF the ignition.
  2. Disconnect the HVAC control assembly connector C2.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ignition 3 voltage circuit of the HVAC control assembly and a good ground.

Does the test lamp illuminate?

Go to Step 11

Go to Step 12

8

Test the blower motor supply voltage circuit between the blower motor and 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 16

Go to Step 9

9

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 16

Go to Step 13

10

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 16

Go to Step 14

11

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 16

Go to Step 15

12

Repair the ignition 3 voltage circuit of the HVAC control assembly. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 16

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13

Replace the blower motor relay.

Did you complete the replacement?

Go to Step 16

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14

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

Did you complete the replacement?

Go to Step 16

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15

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

Did you complete the replacement?

Go to Step 16

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16

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3