I had my tach bounce, especially under strong acceleration, and I thought
the unit was going south, and I was just waiting for it to fail completely.
Then I worked on another--I thought--electrical issue that caused my
alternator
light to flash on and my radio to briefly blink off. One of the first
things I checked and cleaned was the alternator plug, and it seemed OK, but
after
going completely around the circuit I came back to the plug and found that
was, in fact the culprit. Imagine my delight when I realized that securing
the
plug also fixed my bouncing tach.
For what it's worth...
Jay Donoghue
72 B-GT
66 Mustang
In a message dated 4/7/2005 10:09:24 A.M. Eastern Daylight Time,
paul.hunt1@blueyonder.co.uk writes:
Points or some kind of electronic ignition? Could be points bounce, or some
other wear or maladjustment in the distributor, possibly a condenser on the
way out, or an intermittent ground wire in the distributor, or coil wire
where it passes through the distributor body. These last two are
continually flexed back and fore as the points plate moves with changing
vacuum. However all of these are likely to cause misfiring as well, but if
the tach is going *up* rather than down implies *extra* pulses which are
less likely to cause misfiring. A multi-meter with a tach range could tell
you if it is the pulses that are faulty (by also showing higher revs than
should be) or the tach (by indicating the correct) revs. However if it has
better filtering it could indicate steady revs when the tachometer goes
high, even if it is the pulses that are the problem.
PaulH.
----- Original Message -----
> At the high RPM band my Tach started jumping a couple of thousand
> revolutions, at the low band the Tach is pretty steady, is this an
electrical
> problem or is the Tach on it's last leg.
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