I am currently a victim of Chrysler's flawed Climate Control system. The servo is cracked, and it does not function other that when on Defrost. Am I correct in my assumption that heat from the engine bay cracks the plastic base of the servo, causing vacuum to leak out, and causing the servo to not function properly?

I saw a w116 in the junkyard and it had the evil servo. The P.O of the car filled the cracks in the housing with some sort of putty. Would sealing the cracks mysteriously cause the servo to function again, without the vacuum leak? If it's a good idea then maybe I should try it. Most likely the servo is fried and putty won't fix it, and I'll spill antifreeze everywhere by taking it out. When I push buttons on the control panel I hear flaps open if that means anything. I could buy the 700 dollar digital servo and be done with it, buy a servo with an aluminum housing for an unknown amount of money, or a used one that won't last too long. Should I try to "repair" the servo, or forget it and fix it? You will probably suggest the latter but I'm open to ideas .

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1980 240d
1999 SL500

I'm not aware that cracks in the lower housing of the servo cause vacuum leaks. On mine, they caused coolant leaks.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Ditto.

And if there is a coolant leak from the cracked plastic, then the seals on the water valve are likely fried. I autopsied the one on my car. It looked like something that came off the deck of the Titanic when I opened it up. A partially dismantled one at the salvage yard confirmed my findings.

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- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

Can this be repaired? All my servo controls still operate normally I just can't shut off the heat. Can the bottom half of that unit be rebuilt?

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RIP: 80 300SD
RIP: 79 450SEL
2002 E430 4matic (212,000km)
2002 ML500 'sport'

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FACEBOOK: PANZER450

From what I've learned by disassembling a bunch of them, the rubber seal in the bottom that is supposed to stop or limit flow to the heater core has likely disintegrated on you. Parts do not exist for these things, but creativity might get you somewhere.

I have finally given up. I'm just going to buy the digital upgrade for mine if I keep the original ACC controls. I can tune twin SU carbs on a British Leyland nightmare without a hint of frustration, but that monstrosity of a servo is just too stupid to waste time on. I'd rather stab my own eyes out with a rusty tie rod than work on a servo again.

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- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

i took a part a servo apart and to be honest not much to them.

The best way to deal with the problem is to ditch the system completely because something else will fail and will be a money pitt. Convert it to manual climate control or the next gen automatic climate control and youill be all set.

I have a good servo case with no cracks etc if you want.

FS: Assortment of w123 parts

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)