After looking at the service info for the HVAC system for your vehicle , it sounds like your system lost vacuum somewhere ! The position of the mode doors determine where the air comes out at . The doors have vacuum controlled actuators , on the back of the mode switch vacuum lines are connected to it ! To check for vacuum at the switch you'll need to take HVAC control module out of the dash ! There is also a vacuum reservoir or tank under the dash near the HVAC assembly. You could look under the hood in the engine compartment an look for a disconnected vacuum hose from the engine intake manifold !
Step
Action
Yes
No
1
- Start the engine.
- 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 yes
Go to Step 2 no
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 yes
Go to Step 3 no
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 yes
Go to Step 4 no
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 yes
Go to Step 5 no
5
Repair the no vacuum condition.
Is the repair complete?
Go to Step 18 yes
--
6
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
7
- Disconnect the vacuum supply line from the HVAC control vacuum valve.
- 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
8
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
9
Repair or replace the collapsed or leaking vacuum line.
Is the repair complete?
Go to Step 18
--
10
Replace the vacuum reservoir tank. Refer to Vacuum Tank Replacement .
Is the repair complete?
Go to Step 18
--
11
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
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
13
- Disconnect the vacuum line from the actuator.
- Apply an external vacuum source to the actuator.
Did the actuator retract?
Go to Step 14
Go to Step 16
14
With the actuator disconnected, inspect the door for binding.
Does the door move freely?
Go to Step 16
Go to Step 15
15
Repair the binding door. Refer to the appropriate repair.
?€¢
Defroster Door Replacement
?€¢
Mode Door Replacement
?€¢
Recirculation Door Replacement
Is the repair complete?
Go to Step 18
--
16
Replace the vacuum actuator. Refer to the appropriate repair.
?€¢
Defroster Valve Actuator Replacement
?€¢
Mode Actuator Replacement
?€¢
Recirculation Actuator Replacement
Is the repair complete?
Go to Step 18
--
17
Replace the HVAC control vacuum valve. Refer to HVAC Control Vacuum Valve Replacement .
Is the repair complete?
Go to Step 18
--
18
Cycle the HVAC controls through all modes to verify proper operation.
Did you correct the condition?
System OK
--
Hope this helps an good luck !
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