GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C Sierra - 2WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Air Delivery Improper - Auxiliary

Air Delivery Improper - Auxiliary W/O Sunroof

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step tests for auxiliary blower motor that does not operate from the front auxiliary HVAC control assembly regardless of the desired blower motor speed.

    2.

  2. This step tests for a auxiliary blower motor that operates, yet does not accurately respond to the desired blower motor speed from the front auxiliary HVAC control assembly.

    3.

  3. This step tests for an inoperative auxiliary mode actuator in one mode position(s) or in the wrong mode position(s) from the front auxiliary HVAC control module.

    4.

  4. This step tests for an inoperative auxiliary mode actuator in one mode position(s) or in the wrong mode position(s) from the rear auxiliary HVAC control module.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: Air does not flow correctly from the auxiliary air distribution outlets.

1

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

Go to Step 2

Go to Symptoms - HVAC Systems - Automatic

2
  1. Turn ON the ignition, with the engine OFF.
  2. Place the front auxiliary HVAC control assembly blower control in the OFF position.
  3. Place the rear auxiliary HVAC control assembly blower control in the OFF position.

Is the auxiliary blower motor OFF?

Go to Step 3

Go to Blower Motor Always On

3

Place the front auxiliary control assembly blower control in each mode position.

Does the auxiliary blower motor operate at all?

Go to Step 4

Go to Blower Motor Inoperative

4

Does the auxiliary blower motor operate correctly for each mode position?

Go to Step 5

Go to Blower Motor Malfunction

5

  1. Place the front auxiliary HVAC control assembly blower control in the high position.
  2. Place the front auxiliary HVAC control assembly mode control in each mode position.

Does the auxiliary mode actuator operate correctly for each mode position?

Go to Step 6

Go to Step 7

6

  1. Place the front auxiliary HVAC control assembly blower control in the rear control position.
  2. Place the rear auxiliary HVAC control assembly blower control in the high position.
  3. Place the rear auxiliary HVAC control assembly mode control in each mode position.

Does the auxiliary mode actuator operate correctly for each mode position?

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

Go to Step 10

7

Test the mode door control - auxiliary circuit of the front auxiliary HVAC control assembly for an open, a high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 8

8
  1. Disconnect the electrical connector from the front HVAC control module.
  2. Test for resistance between the mode door control - auxiliary terminal and the low reference terminal of the front HVAC control module.
  3. Place the front HVAC control module mode control to each mode position.

Does the resistance change between each selected mode position?

Go to Step 10

Go to Step 9

9

Inspect for poor connections at the harness connector of the front auxiliary 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 13

Go to Step 11

10

Inspect for poor connections at the harness connector of the rear auxiliary 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 13

Go to Step 12

11

Replace the front auxiliary HVAC control assembly . Refer to Auxiliary Heater and Air Conditioning Control Replacement - Front .

Did you complete the replacement?

Go to Step 13

--

12

Replace the HVAC control assembly - auxiliary rear. Refer to Auxiliary Heater and Air Conditioning Control Replacement - Front .

Did you complete the replacement?

Go to Step 13

--

13

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2