Quote:
Originally Posted by Danglerb
Could be bad diaphragms in some of the vacuum actuators. Roger at ************ has replacements for some, others the actuator must be replaced. Check for a vacuum leak, how I have no clue.
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To check for a vacuum leak:
First find the blue check valve that comes from the brake booster. Verify that it works correctly(ie. one way only)
Next, from that check valve, there will be some sort of arrangement of 3 way/5 way/7 way splitters. Find the vacuum line that goes straight through the firewall. Try to pull a vacuum on that line. Chances are, you won't be able to and it will leak which verifies that you have a vacuum leak in you HVAC system. That vacuum line goes straight to a vacuum manifold which is located in the bowels of the console inside the car.
To find out which actuator is leaking, remove the driver's side console panel which will give you visual access under the radio and on top of the engine tunnel. You should see the side of the vacuum manifold there. You can check each actuator without removing the manifold, but the color-coded vacuum lines would each have to be cut one by one, tested, and then spliced back using a vacuum coupler. Doing it this way will allow you to test easily as necessary in the future, but then again, you would be cutting your vaccum lines.
The vacuum manifold can be removed by removing the 3 screws holding it to it's protective cover. It's not extremely difficult to remove these screws, but after you do it once, you'll know why most people just cut the lines and splice them.
The line from the firewall plugs into the hole in the rubber manifold
This view shows how the manifold is set up and also shows the electromechanical switches that are activated by the AC head unit.