GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the Heater Blower Controls System Check?

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Go to Step 2

Go to Heater Blower Controls System Check

2

  1. Place the ignition switch in the RUN position.
  2. Move the temperature control knob from extreme cold to extreme hot one step at a time.
  3. Monitor the temperature control door driving shaft on the back of the temperature control motor while moving the temperature control knob.

Does the shaft move with every knob step movement?

--

Go to Step 3

Go to Step 4

3

  1. The problem is not electrical.
  2. Ensure that the vehicle is reaching the normal operating temperature.

Is the vehicle reaching the normal operating temperature?

--

Go to Step 5

Go to Thermostat Diagnosis

4

  1. Place the ignition switch in the RUN position.
  2. Use a test lampJ 35616-200 in order to backprobe the temperature control motor cavity 10 to ground.

Did the test lamp light?

--

Go to Step 6

Go to Step 7

5

Inspect the temperature control door mechanical condition for binding.

Does any binding exist?

--

Go to Step 16

Go to Step 17

6

  1. Disconnect the temperature control motor.
  2. Connect a test lampJ 35616-200 between the temperature control motor connector CKT 1050 (BLK) cavity 7 and CKT 141 (ORN) cavity 10.

Did the test lamp light?

--

Go to Step 8

Go to Step 9

7

Repair the open in CKT 141 (ORN) between the temperature control motor and S224.

Is the repair complete?

--

Go to Heater Blower Controls System Check

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8

  1. Disconnect the HVAC control module.
  2. Connect an ohmmeterJ 39200 from CKT 1050 (BLK) cavity B at the HVAC control module connector C3 to ground.

Is the resistance less than the specified value?

10 ohms

Go to Step 10

Go to Step 11

9

Repair the open in CKT 1050 (BLK) between the temperature control motor and ground G200.

Is the repair complete?

--

Go to Heater Blower Controls System Check

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10

  1. Connect an ohmmeterJ 39200 between the HVAC control module connector C3 pin B and connector C2 pin F.
  2. Move the temperature control knob from extreme cold to extreme hot.

Does the resistance vary within the specified range?

0-10 Kohms

Go to Step 12

Go to Step 13

11

Repair the open in CKT 1050 (BLK) from the HVAC control module to G200.

Is the repair complete?

--

Go to Heater Blower Controls System Check

--

12

Use an ohmmeterJ 39200 in order to measure the resistance from the HVAC control module connector C2 CKT 733 (LT BLU) cavity F and the temperature control motor connector CKT 733 (LT BLU) cavity 8.

Is the resistance less than the specified value?

10 ohms

Go to Step 14

Go to Step 15

13

Replace the HVAC control module.

Refer to Heater Module Replacement - Auxiliary.

Is the replacement complete?

--

Go to Heater Blower Controls System Check

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14

Replace the temperature control motor.

Is the replacement complete?

--

Go to Heater Blower Controls System Check

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15

Repair the open in CKT 733 (LT BLU) between the HVAC control module and the temperature control motor.

Is the repair complete?

--

Go to Heater Blower Controls System Check

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16

Repair the cause of the binding.

Is the repair complete?

--

Go to Heater Blower Controls System Check

--

17

Repair restriction in coolant flow.

Is the repair complete?

--

Go to Heater Blower Controls System Check

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