Cruise control works once in awhile.
No response when control stalk is pushed to set. Sometimes the cruise will engage - I find out when I let up on the gas and realize the it is engaged and working, sometime after an attempt is made to activate it. When it works, it is steady when there is a slight load on the engine but kindof jerky otherwise.
Also noticing the tach is intermittent - if this has anything to do with the cruise control.
I'm suspecting a vaccuum leak somewhere or a or a problem with the linkage.
Ofcourse the MB dealer says the control unit, at $600 to replace it. They say it's routine, and I believe it, but would like to rule out other causes first.
Thanks for your help.

The control unit is probably at fault. We sell them in the partshop. The tach is probably the diagnostic plug housing is faulty and will need a new one. We have those too.

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

Thanks -
re - diagnostic plug housing is faulty.

I cleaned the contacts and screwed back on and was working steady for awhile.
Are you talking about the main round thing that screws in or the receiving part that's mounted to the fender ?
Or is it both the male/female assembly as a whole ?

Just the part that plugs in and can be removed.

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