GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C Sierra - 2WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 High or Low Temperature Control Effort

Step

Action

Yes

No

1

Were you sent here from Symptoms or another diagnostic table?

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

2

Is one of the following a concern of the customer:

    • The mode control operates with little or no resistance.
    • The HVAC outlet air is constant, regardless of the mode control setting.
    • While driving the vehicle the mode control setting changes.

Does the mode control operate too freely?

Go to Step 3

Go to Step 7

3

With the ignition in the ON position:

  1. Select the HIGH blower motor speed.
  2. Cycle the mode control through all of the settings.

Does the air outlet change through all of the modes?

Go to Step 16

Go to Step 4

4

Inspect the connections of the mode control cable.

Is the mode control cable disconnected from the mode actuator?

Go to Step 15

Go to Step 5

5

Inspect the mode control cable and linkage, while operating the mode controls.

Does the mode actuator move while operating the mode controls?

Go to Step 21

Go to Step 6

6

Inspect the cable casing while operating the mode controls.

Does the cable casing move, instead of the cable, while operating the mode controls?

Go to Step 18

Go to Step 21

7

Inspect the HVAC control assembly for any debris or obstructions that would increase the effort to operate the mode controls.

Are there any obstructions?

Go to Step 20

Go to Step 8

8
  1. Disconnect the mode control cable from the mode actuator.
  2. Operate the HVAC control assembly with the mode control cable disconnected.

Does the HVAC control assembly bind now?

Go to Step 10

Go to Step 9

9

With the mode control cable disconnected:

  1. Manually operate the mode actuator.
  2. Inspect for binding.

Does the mode actuator bind with the cable disconnected?

Go to Step 19

Go to Step 10

10
  1. Disconnect the mode control cable from the HVAC control assembly.
  2. Operate the HVAC control assembly with the cable disconnected.

Does the HVAC control assembly bind now?

Go to Step 16

Go to Step 11

11

With the mode control cable disconnected at both ends:

  1. Extend the cable in both directions.
  2. Inspect the cable for binding.

Does the mode control cable bind?

Go to Step 17

Go to Step 12

12
  1. Inspect the mode control cable for kinks or bends from incorrect routing.
  2. Repair the cable or routing as necessary.

Does the mode cable still bind?

Go to Step 17

Go to Step 13

13

Operate the HVAC control assembly with the mode control cable disconnected.

Does the HVAC control assembly bind now?

Go to Step 16

Go to Step 14

14

Reassemble the mode control system.

Is the action complete?

Go to Step 21

--

15

Reconnect the mode control cable to the mode actuator linkage install the cable retainers.

Is the action complete?

Go to Step 21

--

16

Replace the HVAC control assembly. Refer to .

Is the repair complete?

Go to Step 21

--

17

Replace the mode control cable. Refer to Mode Control Cable Replacement in HVAC Systems - Manual.

Is the repair complete?

Go to Step 21

--

18

Secure the mode control cable casing.

Is the action complete?

Go to Step 21

--

19

Repair the binding door. Refer to the appropriate repair:

Is the repair complete?

Go to Step 21

--

20

Remove the debris.

Is the action complete?

Go to Step 21

--

21

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2