Bob, I would guess that you have one of two possibilities.
The new ignition is putting out a very short spike (or spikes) like an MSD
(multi-spark discharge). The spikes may not be long enough for the tach to
register. If you look inside the tach you will find several capacitors that
basically filter the signal coming from the dizzy. One of the functions of the
caps is to filter out the bounce of the points. They may be filtering the short
spikes.
There is also the possibility that the voltage to the points is not what is used
to be. If the Crane is has wires to the dizzy, (no wires to the ignition voltage
or battery) it could be putting out only a few volts. The tach may not have
enough voltage to provide a full deflection of the needle.
I would put a call in to Crane and ask some questions. Tell them your problem.
They have most likely seen this situation before.
Vic Whitmore
76 Spitfire
Thornhill, Ontario
Bob Norway wrote:
>
> All,
>
> Still having problems with my Tach since I replaced the Lucas Electronic
> Ignition with the Crane HI6500 amp module and Crane PS20 coil. (No dizzy
> mods required)
>
> The tach will not read above about 1500 rpm and when the engine goes
> above that it actually will come down some. Seems (key word: SEEMS) to
> work OK at idle RPM (at least my calibrated ear hears 800-900 RPM and
> that is what the tach reads)
>
> Tried using my Sears Shop Tach and get the same results. Even
> disconnected car tach and tried shop tach alone.... no joy, same
> problem.
>
> Don't ask if I tried the old coil.... alas, it's gone to dumpster
> heaven.... (sigh)
>
> Any and all help/ideas welcome.....
>
> Cheers,
> --
> Bob Norway
> Rockledge, Florida
> Home Page http://www.geocities.com/CapitolHill/Lobby/5953/mypage.html
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