My center vents with A/C on are intermittent in operation, blowing when the interior is hot and not when car is just warm. Which is more likely to fail like this , the vacuum servo, switchover valve or maybe the control unit ?

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David McDonald
1985 300TD

I have replaced many vacuum servo units lately. It is very easy to check with a hand held vacuum pump/tester.

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Benzmac:
Donnie Drummonds
1991 GMC Syclone
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Well????
 

So what fixed the problem? We're having the exact same problem in our '84 300TDt and I liked to fix it. What's the deal?

I haven't fixed it yet. I just haven't got around to removing the glove box again.