I finally got around to installing a tach in my 82 Westy 1.9TD. I used a
tach from a 1984 VW Quantum TD and a tach equipped instrument cluster
from an 85 gas engine Vanagon. I removed the gas tach and installed the
diesel tach in it's place. I had to use the tach housing from the
vanagon gas tach. Only the bare instrument w/dial came from the Quantum
TD. I had to change the wiring pin locations in the 14 pin harness to
the cluster as for some reason VW changed all but 1 of the wire
positions when they went from an analog clock to a tach. My alternator
had a "W" lead so I connected a wire from it to the otherwise unused
tach pin on the 14 pin harness connector. The 82 dash had 2 brown ground
wires but the new style cluster only needs 1. I cut 1 brown wire off
leaving a couple of inches on the pin. I soldered this brown wire to the
other one and I used the leftover pin with short wire stub for the tach
lead from my alternator "w" connector. I used the pin position for the
OX led to connect the wire that used to connect to the GLOW plug led.
The red OX led now functions as my glow plug led. I will correct this
label and install a yellow led soon. I bought another diesel tach on
Ebay and I am going to try to install this one into the 82 Diesel
instrument cluster and if this works it will solve the problem of the
color and label for the GLOW led. For changing the wire locations in the
14 pin connector I used the wiring instructions written up by David
Beierl and posted on the Vanagon list. The Quantum tach is calibrated
for the pulley ratios of the Quantum alternator. It was way off from the
needs of the Vanagon pulley system. I anticipated this and while I had
the tach out of the housing I drilled a small hole in the back of the
housing. This hole lines up with an adjustment pot in the tach. I can
just reach it with a small screwdriver and change the setting as needed.
I used a tranny gearing chart and measured the circumference of my
wheels. I then calculated the engine rpm at 65 MPH in 4th and adjusted
the pot a few times until it was right.

Mark