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Re: Tach problem

To: mgs@autox.team.net
Subject: Re: Tach problem
From: ATWEDITOR@aol.com
Date: Thu, 7 Apr 2005 10:56:28 EDT
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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