1. Start the engine.
2. Turn the blower motor fan ON and select an air outlet mode.

Does air flow out of the selected HVAC outlet ducts?

Go to Step 3

Go to Step 2

Did the customer concern mention that the air discharges out the correct ducts at first, but then changes during higher engine RPM?

Go to Step 7

Go to Step 3

With the engine running, cycle the HVAC controls through all the modes.

Does the air come out of the selected outlet ducts?

Go to Step 18

Go to Step 4

With the engine running, take a vacuum reading at the manifold vacuum port that supplies vacuum to the HVAC control vacuum valve.

Is there engine vacuum?

Go to Step 6

Go to Step 5

Repair the no vacuum condition.

Is the repair complete?

Go to Step 18

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Take a vacuum reading at the vacuum supply line at the HVAC control vacuum valve.

Is the vacuum reading the same as the engine vacuum?

Go to Step 11

Go to Step 8

1. Disconnect the vacuum supply line from the HVAC control vacuum valve.
2. With the vacuum gauge connected to the vacuum supply line, re-start the engine and turn the engine OFF.

Does the A/C system lose vacuum after turning OFF the engine?

Go to Step 8

Go to Step 11

Inspect for leaking or collapsed vacuum lines between the engine manifold vacuum port and the HVAC control vacuum valve.

Are the vacuum lines leaking?

Go to Step 9

Go to Step 10

Repair or replace the collapsed or leaking vacuum line.

Is the repair complete?

Go to Step 18

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Replace the vacuum reservoir tank. Refer to Vacuum Tank Replacement .

Is the repair complete?

Go to Step 18

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Using an external vacuum source, apply vacuum to the appropriate vacuum line at the HVAC control vacuum valve connector. Refer to HVAC Vacuum Schematics .

Does the actuator retract?

Go to Step 17

Go to Step 12

Inspect for leaking or collapsed vacuum lines between the actuator and the HVAC control vacuum valve connector.

Are the vacuum lines leaking?

Go to Step 9

Go to Step 13

1. Disconnect the vacuum line from the actuator.
2. Apply an external vacuum source to the actuator.

Did the actuator retract?

Go to Step 14

Go to Step 16

With the actuator disconnected, inspect the door for binding.

Does the door move freely?

Go to Step 16

Go to Step 15

Repair the binding door. Refer to the appropriate repair.

Is the repair complete?

Go to Step 18

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Replace the vacuum actuator. Refer to the appropriate repair.

Is the repair complete?

Go to Step 18

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Replace the HVAC control vacuum valve. Refer to HVAC Control Vacuum Valve Replacement .

Is the repair complete?

Go to Step 18

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Cycle the HVAC controls through all modes to verify proper operation.

Did you correct the condition?

System OK

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