Every water cooled Vanagon has a Hall Effect sender. My 83.5 and 84 have it.
If you need a signal from the Hall Effect sender for the purposes of driving
a RPM gauge you can take the signal at the terminal 15 of the ignition coil.
You can isolate it with a 0.1 or 0.01 uf 250V capacitor put in serial to the
line to the RPM gauge. The capacitor will block DC off but pass the pulses
through for the RPM gauge. You may need to experiment with the capacitor
to see if the capacitance is too low. My guess is anywhere between 0.1 and
0.01 uf will work fine. The capacitor may not be needed at all if the RPM
gauge has a signal conditioning circuit to deal with the DC component in the
signal coming from the terminal 15.

David

--- Dan Barrett <dbx@POBOX.COM> wrote:

> Mark,
>    Re. where to find a hall effect sender: without my Bentley close to
> hand, I seem to recall that the distributor on post-86 buses has a hall
> effect sender on it.
>
> Best,
> d.
> 1990 GL -- "Mudskipper"
>