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w123 - complete climate servo bypass with a/c

9116 Views 14 Replies 6 Participants Last post by  UncleDirtnap
I've read every climate and servo thread I can find, but still don't have enough to piece together what I need.

First, the car - 1980 300cd, 110k. It's solid but the florida sun and 20 years under an oak tree has left it with some rust, terrible rubber, and lots of neglect. It's my daughter's 'learn to work on cars and drive it when I'm 16' car. It's nice enough to be nice but not nice enough to restore, if that makes any sense.

The climate control system is toast. Defrost comes on, but that is it. The servo was a solid corroded mass of nonsense inside - no moving parts inside at all, like something recovered from the titanic. I removed the servo and plumbed the heater core in manually.

Now that the days are in the 90s, I need to go the other direction and have some AC, but this is where I can't quite find the info I need. I have a handful of colorful vacuum lines, the electrical connection to the servo, and a bunch of questions.

Does someone have a document that details the outcomes of the buttons? i.e push bottom button, green and red wires get power, and vacuum goes to yellow and blue? I know that the servo controlled things like fan speed and recirculation, but the rest should be constant.

If I can push a button, have the fan come on full, air route to the vents, and the AC come on, then I will be happy.

Ultimately, it would be fun to reverse engineer part of the servo with an arduino and some small vacuum selenoids, but thats later on.

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This guy makes and sells electronic replacements of evil servo: It works and he is extraordinarily helpful and knowledgeable.
They are behind the center set of switches and some are behind the AC controls. If memory serves (and at my age, it probably doesn't so double check this), there are vacuum switches and they energize some vacuum actuators?? The switches are behind the dash panel switches and the vacuum actuators are behind the AC control module (very hare to get out and back in). Search for vacuum control diagrams. There are some that will show where everything is located. Good luck!
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