Do you have an after-market electronic ignition system or trigger in the car
already? These can often cause the early current pulse tach to read high.
If so, or in any case, check the pickup on the back of the tach, which
should be on the outside on yours. The white trigger wire should make one
complete loop of the pickup i.e. through the middle, round the side, then
through the middle again. Make sure it doesn't go round twice and through
three times and if so correct it. If it still does it, or if it only goes
through twice and round once anyway, change it so it just goes through once
and not round at all and try that.
If you have points then it could be points bounce or some other problem with
the ignition LT that might be difficult to find short of changing components
willy-nilly. If it always did it it could be an internal electronics
problem like a faulty timing resistor or capacitor. You could try
diagnosing that, but you may find you have more problems when you install
the new ignition system so I'd do that first and only *then* tackle the
tach, as that could cure it anyway. If you still have problems then the
later voltage pulse tach (used from 73 on) usually gets over problems
associated with different ignition pulses, and of course would solve the
problem if it is internal to the tach.
PaulH.
----- Original Message -----
> The tach has always read about double what the actual revs are. Tried a
> new
> voltage regulator and it fixed the problem with the other gauges, but not
> the tach.
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