GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value

Yes

No

1

Did you perform the Heater Blower Controls System Check?

--

Go to Step 2

Diagnostic Starting Point

2

Check the attachment of all vacuum lines between the heater module and the control assembly.

Are the vacuum lines connected?

--

Go to Step 4

Go to Step 3

3

Connect the vacuum lines.

Is the repair complete?

--

Go to Diagnostic Starting Point

--

4

  1. Disconnect the vacuum line from the actuator at the crank pin.
  2. Check the air control valve travel and effort.

Is there proper valve travel and effort?

--

Go to Step 5

--

5

  1. Connect the vacuum hose.
  2. Start the vehicle in order to assure adequate vacuum.
  3. Watch the actuator at the heater module while moving the mode knob.

Does the actuator move?

--

--

Go to Step 6

6

Inspect the control assembly for the following conditions:

    • Poor connections
    • Broken, pinched, kinked or otherwise damaged vacuum lines

Are the connections and vacuum lines OK?

--

--

Go to Step 7

7

Repair any damaged vacuum lines or poor connections at the control assembly, as necessary.

Is the repair complete?

--

Diagnostic Starting Point

--