Al:

    The cruise control is covered in the Bentley manual in detail.  There are
several steps to check when troubleshooting:

1.    Vacuum:  Disconnect the vacuum line at the pump port, collapse the vacuum
servo that pulls on the throttle, then put your finger over the end of the
disconnected hose and see if the servo returns to the relaxed position.  If yes,
there is a leak; if no, go to next step.

2.    Check electrical components, including:
    a.    Inductive generator on the speedo by the cable.  Small connector with two
wires.
    b.    Control unit.  Lives in dash, under and to the right of instrument
cluster.
    c.    Vacuum Pump.
    d.    Switch stalk at steering wheel.
    e.    Others that I can't remember.

    The test procedures usually involve the multipin connector to the control unit,
and they have you apply test the various pins, then look for a result, such as the
pump operating, 12 volts positive, open or closed circuits, etc..

    I had this trouble last month, and all the tests are easy to do.  The trouble
was that the inductive pickup connector was not installed right (operator error).
        Hope that helps.
                            Randy

Al Knoll wrote:

> Piqued my interest.  Just what information does the VW stock 89 cruise control
> get and where does it get it.  Motor speed via tachometer?  Driveshaft rotation?
> How does it know how "fast" the venerable beast is going?  I recently had a
> miserable experience with an alarm installer who botched a bunch of things on
> the van.  Tach no longer works, speedo cable ripped off the speedo, broken tab
> on the instrument cluster housing so the cover rattles etc etc.
>
> And of course the autopilot doesn't work now.  So what should I check to see
> what other damage they've done re the cruise control.  It would help if I knew
> what signals the CC uses and from where they originate.
>
> Any help is of course appreciated.
>
> al_knoll@hp.com
>
> 89 Westie syncro