[Vwdiesel] Erratic Tach
Roger Brown
r.c.brown at ieee.org
Thu May 31 19:20:05 EDT 2007
Dave Heart wrote:
> Has anyone come across a stock jetta gasoline tach that works fine for
> about 15 minutes then becomes jumpy and finally stops? Always works fine
> when engine is cold. I have been using Roger Browns basic design to
> allow cruise control and gasoline tach in my camper diesel pickup. Have
> tried relocating electronics away from engine heat to no avail. The
> jetta tach was a used one.
Two likely causes would be the voltage stabilizer on the back of the cluster PCB. Do the
other gauges work fine? Other thing might be a loose wire at the back of the tach, maybe
the vibration gets to it with engine operation.
On my '82, I once had the tach cut out and I thought it was heat related (on the way to
Las Vegas). Turns out the power or ground wire connection I made at the injector pump was
loose and I guess with the heat and vibration, it would cut in and out. Tightened the nut
back down and it was fine.
--
Roger
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