when I turn on the a/c in my 300d nothing happens until I begin to accelerate. At about 15 mph it finally kicks in and works fine the rest of the ride. How can I isolate the vaccum leak that is causing this to occur. I think it may be related but the auto door locks donlt work either except the rear driver door always unlocks while driving.

any help appreciated

Providing the year model would certainly help narrow things down.

sorry, '77 300d

Do you center vents work?

If not then you may have a leaky accuator.

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center vents work fine

Check the vac line that supplies the ACC. In my 82 it is a green line with a yellow stripe I believe, and it goes through the firewall. See if it hold vac. This should tell you if it is vac related or not. If all the vent work like they are supposed to it probably isn't a vac problem.

Have you checked to see if the AC belt is tight enough? Maybe it's slipping.

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Find the LOCK actuator that is leaking and you've probably solved your problem with the A/C. See search, for Mitivac and door locks, for isolation and determination techniques.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)