I have a 1979 300SD. Its a sweet car, and I am preparing to sell it. It only has 130K original miles. Anyway, I cant seem to get the climate control sysyem to function properly. First, heres whats been replaced: servo (rebuilt/ stainless, 5 button push buttons, amplifier checks good). the air conditioning has been retrofitted and works excellent, however the a/c will not turn off at the switch, only if I turn off the blower. THE SWITCH is GOOD. I have taken it apart and cleaned it, its just like the power window switch, and I'm familiar with the symptoms of corroded switches. I dont know why it wont shut off at the switch, there is no indication of anyone attempting to straight wire to bypass a defective amplifier. Also, having mentioned replacing the 5 button switch, the defrost and bi-level dont work at all, and high blow only works, low blow setting blows high.This is the most absurd climate control design I have ever messed with. Anyone have any insight on where I might start to rectify this climate control fiasco??? Thanks Dave (407) 716-6212...by the way the car is for sale 3500...new windshield, new front/rear window gaskets, new rear bilsteins, euro headlights, no rust whatsoever, excellent interior, perfect dash, new hirchmann aftermarket antenna, kenwood cd player,new tumbler with key,nice car, climate control funky.

With all of the screwy smptoms at once I would suggest to inspect the bundle of hard plastic vacuum lines where it runs under the battery tray on the way to the servo. Leaking battery acid corrodes the vacuum lines eventually compromising the lines allowing the system to suck the acid into the rest of the system making everything screwy. It is not a pretty scenario when this is the problem. Heck it's not a pretty scenario when that system works properly. We joke around the shop that when one doesn't work it needs the genie in the bottle replaced that made it work in the first place.