Gregory,

Besides the vacuum lines in the engine compartment, there is a long
rubber line that goes to the driver's compartment to switches on both
the clutch and brake pedals. The switches on the pedals are dual
function switches, the shut off the cruise control by cutting off
both the vacuum and power to the system. You can access the switches
by removing the cover piece on the steering wheel shaft.

A quick way of testing the front switches is to find the "T" piece on
the vacuum line in the engine compartment next to the vacuum pump and
crimp off that line. Take your van for a ride and see if the cruise
control works. If it does, then the vacuum leak is more than likely
at the pedals. Sometimes, the rubber vacuum hose gets brittle where
they attach to the pedal switches, and it can be a simple matter of
trimming the ends of the hose.

If it is not a vacuum problem, then it might be a simple matter of
adjusting the switches at the pedals.

Ric

At 01:37 PM 2/6/2008, Gregory Smith wrote:
>Hi Gang,
>
>My '88 has a factory installed cruise control system which is having
>difficulty maintaining speed.  It works at first and then it's ability
>falls off quickly, in less than a minute, as if it is losing vacuum.  I
>have check the vacuum lines that I can see connecting to the system,
>but I'm not 100% sure I know what all in included.
>
>Can anyone point me to an online diagram that covers the system?  In
>particular in the rear.  For instance I don't know what the device in
>the right rear corner (just to the left of the taillight) with vacuum
>lines and a wire harness going to it is.  It has a vacuum line going to
>it (connects to the throttle servo), but there is an unused nipple just
>below the one that has the line on it, perhaps it needs to connect to
>something?
>
>ANY tips are appreciated.
>
>Ciao,
>Gregory Smith
>Olympia, WA
>'87 Bertone X1/9 Corsa
>'88 VW Vanagon