Mercedes: cruise control, mercedes 240d, vacuum switch

Question
Mercedes 240D,'79,automatic transmission. When the cruise is
engaged I notice and feel a constant slight surge, almost as
though the cruise is struggling to regain vacuum. Also, I must be
losing some vacuum that operates the central locking system
because there should be enough stored vacuum to operate the
door locks at least 10 times before the resevoir is empty and
when the car sets overnight, I can try to lock the doors the next
morning without starting the car and they will not operate. Do
the check valves ever go bad and what about the vacuum switch
inside the driver's door?

Answer
Cruise Control Repair Articles
http://www.mercedesshop.com/shopforum/showthread.php?p=883130#post883130


Diagnosis of the central locking system covers hundreds of pages, I suggest you join:
ShopForum > Technical Information and Support  
Diesel Discussion  
http://www.mercedesshop.com/shopforum/forumdisplay.php?f=15

Do a search on "central locking system"...