GM Service Manual Online
For 1990-2009 cars only

Blower Motor Inoperative at Any Speed Front

Circuit Description

The airflow is controlled by modulating the commanded blower voltage that varies the blower speed. Under automatic control, the blower adjustments are made based upon the following factors:

    • The vehicle speed
    • The coolant temperature
    • The sun load sensor

Special cases exist that may override the normal operation of the blower in order to limit the following conditions:

    • Snow ingestion
    • Purging the air ducts
    • Cooling the instrument panel cluster
    • Enhancing the heater warm-up performance

Test Description

If the blower is inoperative in the normal operating procedure, but operates properly in override, the IPC or the data line between the IPC and the heater and A/C programmer are suspect.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. Turn the key to the ON position.
  2. With the engine running, connect the Scan Tool .
  3. Set the blower on high (99%).
  4. Use the Scan Tool in order to display HVAC DATA, BLOWER MOTOR %.
  5. Change the blower speed. Observe the change in speed as the numbers decrease.

Did you complete the procedure?

--

Go to Step 3

--

3

Is the blower non-operational or intermittent?

--

Go to Step 6

Go to Step 4

4

Does the blower speed consistently decrease at a gradual rate from 99 to approximately 30, and then stop?

--

Go to Step 7

Go to Step 5

5

Is the blower speed consistent, then OFF?

--

Go to Step 8

--

6

  1. Use a Scan Tool in order to view the blower speed.
  2. Command the blower to the HI speed (100%) using CCP.
  3. Command the blower to the LO speed (42%).

Does the commanded value equal the displayed value on the Scan Tool ?

--

Go to Step 10

Go to Step 9

7

The blower is operating properly.

Inspect for improper temperature control.

Did you inspect for improper temperature control?

--

Go to Step 18

--

8

  1. Exit the diagnostic.
  2. Start the engine.
  3. Select the LO blower.
  4. Measure the voltage at blower connector B.

Is the voltage greater than the specified value?

9 V

Go to Step 17

Go to Step 13

9

  1. Use the Scan Tool in order to view the blower speed.
  2. Set the A/C system to 75° AUTO.
  3. Increase or decrease the set temperature.

Is the blower speed (%) within the specified value?

40-100 %

Go to Step 10

Go to Step 11

10

Measure the voltage at the blower motor connector B.

Is the voltage less than the specified value?

4 V

Go to Step 13

Go to Step 12

11

Replace the heater and A/C programmer. Refer to Programmer Replacement .

Is the repair complete?

--

Go to Step 18

--

12

  1. Disconnect the blower.
  2. Inspect the resistance of connector C to the battery voltage.
  3. Inspect the resistance of connector A to ground.

Is the resistance greater than the specified value?

1.0 ohms

Go to Step 14

Go to Step 15

13

  1. Inspect CKT 754.
  2. If CKT 754 is OK, replace the heater and A/C programmer. Refer to Programmer Replacement .

Did you complete the repair?

--

Go to Step 18

--

14

  1. Inspect the fuse.
  2. Repair CKT 542 as required. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

15

  1. Turn the key OFF.
  2. Measure the resistance between connector A and ground.

Is the resistance less than the specified value?

50 ohms

Go to Step 19

Go to Step 20

16

Replace the blower motor assembly. Refer to Blower Motor and Fan Replacement .

Did you complete the repair?

--

Go to Step 18

--

17

Set the blower speed to HI.

Does the voltage change to less than the specified value?

4 V

Go to Step 16

Go to Step 13

18

  1. Use the Scan Tool in order to clear the DTCs.
  2. Verify proper operation of the system.

Did you clear the DTCs and verify the operation?

--

Go to Diagnostic System Check

--

19

Inspect CKT 50 for an open. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Diagnostic System Check

--

20

  1. Turn the key off.
  2. Measure the resistance between connector B and ground.

Is the resistance less than the specified value?

250K ohms

Go to Step 13

Go to Step 16

Blower Motor Inoperative at Any Speed Rear

Circuit Description

Power is available from the CONSOLE fuse through the switch to the blower motor and ground. A series of 3 resistors contained in a module vary the circuit amperage that controls the blower speed. The heater and A/C programmer receives a feedback voltage signal, but this has no effect on the rear blower operation.

Test Description

The numbers below refer to step numbers on the diagnostic table.

  1. If CKT 52, CKT 850, and the HI position have continuity, the measurement will be near zero. As slower speeds are selected, the ground path of the blower motor passes through more resistors in the module. More resistors in the ground path increases the voltage at S345. Turn off the rear blower switch in order to measure the voltage.

  2. If a resistor in the module is open, all of the cavities beyond that resistor will also be open. If cavity E operates the blower, then the fault is in the switch or in the wiring to the switch.

Step

Action

Value(s)

Yes

No

1

Did you perform the Functional Check?

--

Go to Step 2

Go to Functional Check

2

  1. Turn on the ignition while leaving the engine off.
  2. Turn the rear blower motor switch to each setting.

Does the rear blower motor operate in any setting?

--

Go to Step 6

Go to Step 3

3

  1. Turn the rear blower motor switch to the HI position.
  2. Measure the voltage at connector A of the rear blower motor. Refer to Measuring Voltage in Wiring Systems.

Does the voltage measure near the specified value?

B+

Go to Step 4

Go to Step 7

4

  1. Remove the rear cover of the center console.
  2. Disconnect cavity A of the rear blower motor switch connector.
  3. Measure the resistance at cavity A and ground. Refer to Testing for Continuity in Wiring Systems.

Does the resistance measure within the specified range?

0-1 ohms

Go to Step 5

Go to Step 12

5

Connect a test light across the harness terminals A and B. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Did the test light illuminate?

--

Go to Step 10

Go to Step 13

6

  1. Remove the rear cover of the center console.
  2. Disconnect the rear blower motor switch harness connector.
  3. Connect a fused jumper between the following cavities of the rear blower motor switch connector and ground:
  4. • Cavity B
    • Cavity C
    • Cavity D
    • Cavity E

Refer to Using Fused Jumper Wires in Wiring Syetems.

Does the blower motor run at the correct speeds?

--

Go Step 8

Go to Step 9

7

  1. Inspect the CONSOLE fuse for an open.
  2. If the fuse is blown, test CKT 41 for a short to ground. Refer to Testing for Short to Ground in Wiring Systems.
  3. Repair the short to ground in CKT 41.
  4. Verify that the current draw of the blower is within the specified range. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

0-6 amperes

Go to Functional Check

Go to Step 11

8

Inspect for faulty connections/terminal tension at the rear blower motor switch connector. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Functional Check

Go to Step 16

9

  1. Inspect for faulty connections/terminal tension at the rear blower resistor module connector. Refer to Connector Repairs in Wiring Systems.
  2. Test for wiring continuity between the rear blower motor resistor module and the rear blower motor switch. Refer to Testing for Continuity in Wiring Systems.
  3. Repair the wiring as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and repair the condition?

--

Go to Functional Check

Go to Step 15

10

  1. Inspect for faulty connections/terminal tension at the rear blower switch connector. Refer to Connector Repairs in Wiring Systems.
  2. With the ignition off, use a test light in order to verify CKT 52. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Did the test light illuminate?

--

Go to Functional Check

Go to Step 14

11

  1. Test the CKT 41 for an open. Refer to Measuring Voltage in Wiring Systems.
  2. Repair the open in CKT 41. Refer to Wiring Repairs in Wiring Systems.

Did you find and repair the condition?

--

Go to Functional Check

--

12

  1. Test for an open in CKT 850. Refer to Wiring Repairs in Wiring Systems.
  2. Repair the open in CKT 850. Refer to Wiring Repairs in Wiring Systems.

Did you find and repair the condition?

--

Go to Functional Check

--

13

  1. Test for an open in CKT 52 between S345 and the rear blower motor switch. Refer to Wiring Repairs in Wiring Systems.
  2. Repair the open in CKT 52. Refer to Wiring Repairs in Wiring Systems.

Did you find and repair the condition?

--

Go to Functional Check

--

14

  1. Test for an a short to voltage in CKT 52. Refer to Wiring Repairs in Wiring Systems.
  2. Repair the short to voltage in CKT 52. Refer to Wiring Repairs in Wiring Systems.

Did you find and repair the condition?

--

Go to Functional Check

--

15

Replace the resistor module.

Did you complete the repair?

--

Go to Functional Check

--

16

Replace the rear blower motor switch.

Did you complete the repair?

--

Go to Functional Check

--