05-16-2006, 01:49 AM
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Registered User
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Join Date: Jun 2001
Location: Santa Monica, CA
Posts: 2,053
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I saved this in my folder from an unknown source:
Quote:
Located somewhat above and behind the climate unit are the five vacuum valves which activate the various vacuum motors, which in turn direct air flow in your car. Each valve has a rubber vacuum hose connection and an electrical connection as well.
From left to right, they are: defroster door, leg door, center panel vent door, fresh/recirc door, and main air door.
Here's how the change works. The main air door is open only when vacuum is applied. The fresh/recirc door is open only when vacuum is *not* applied - they're opposites. Connecting both to the same vacuum source will cause one or the other - but not both - to be open at any time. The result is either 100% fresh air or 100% recirculated air. The vacuum valve intended for the fresh/recirc operation supplies an appropriate source.
Remove the rubber vacuum hoses for both the main air door and the fresh/recirc door from their respective vacuum valves. Push a short length of your new rubber vacuum hose onto the valve for the fresh/recirc function - second from right. Add the tee fitting to the end of this hose. Plug both the hoses for the main air door and fresh/recirc door into the tee. Then disconnect the electrical connector for the main air door from its vacuum valve, which is no longer used.
That's it, you're done. There is one change you may notice after this conversion. The main air door immediately flops open or closed when vacuum is applied or released, respectively. The fresh/recirc door, on the other hand, is heavily damped - it requires a few seconds to move from one extreme to the other. Hence when changing from fresh air to recirculated air, there is a short period of time when essentially no air flow is permitted. During this time, you can hear the blower fan change pitch, with perhaps a bit of a whistle as the recirc door begins to open. Such a change takes place when you switch from EC mode (which is always fresh air) to AC mode. Consider it one method through which to verify your work.
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FWIW 
__________________
The Golden Rule
1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)
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