What year Jag? The 71 B had a current pulse tach, this changed to a voltage
pulse type in 73. Maybe the Jag changed at about the same time, has a
voltage pulse type, and these are less susceptible. But any electronic
ignition frequently causes tach problems. I have seen waveforms of
Pertronix ignition and it had a much longer period of oscillation or 'noise'
than standard points. This noise will cause multiple pulses at the tach,
and if the duration exceeds that which the tach is expecting it will cause
high readings.
----- Original Message -----
From: <bill.marianna.graham@attglobal.net>
To: <mgs@autox.team.net>
Sent: Sunday, June 01, 2003 12:21 AM
Subject: Ignitor effect on tach
> I just had an Ignitor installed in the distributor of my 71 B roadster.
> Now my tach in reading extemely high. For example, it now reads 4000 rpm
> at 52 mph rather than about 2900 it should. I've had an Ignitor in a Jag
> for 6 years with no problems. Any suggestions on how I get the tach back
> to normal?
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