[Vwdiesel] a meta-bentley question

[Shalyn Shourds]

    Since this has come up....  I recently took the old '85
Jetta TD on a 2861 mile trip across the southern US.
Somewhere in Eastern Tennesee, the tachometer started
dipping.  I pulled over and tightened the belts thinking it
was the alternator belt slipping.  It wasn't.  Pulled over
again and messed with the wires some and the tach totally
died.  About the same time, when I checked inside the cab to
see if the tach had come back to life, I saw that the "buy a
new engine" (oil pressure) light and buzzer were in full
force.  I eventually regained my courage and figured it was
an electrical problem, jiggled the wire on the oil cooler
sensor and it went away.  I still have no tachometer,
though.  I looked into Bentley, but the wiring diagram stops
at a black box.  Anyone know what kind of output I should be
getting at the W terminal at idle--a steady voltage, some
kind of alternating current?  Or, anyone know where the wire
goes after it enters the firewall?

        I appreciate any guidance.  The car runs fine, but I
bothers me to see that tach needle dead on zero.  Car ran
great on the
rest of the trip.  Only creepy part was realizing I was the
oldest car on the highway.  Even older than the cars on the
side of the road.  I guess that's a good thing, though.

        -Shalyn

        '85 Jetta TD 270,000 mi.