[Fot] electric tach to fit TR4 tach body?

[Bill Babcock]

actually, a surprising number of automotive devices won't work well at 12
volts.
On Dec 4, 2009, at 3:40 PM, Randall wrote:

>> My experience with the electric tach conversion in my TR4A is
>> that the tach is not very happy. I wasn't able to do careful
>> measurements but the little that I did led me to believe that
>> the voltage was likely to drop *below* the critical voltage
>> of whatever regulator is now inside the tach shell!
>
> Very possibly, my point was just that I don't think an alternator
conversion
> is going to fix that; unless your alternator puts out enough at idle to
keep
> up with the maximum load.  Even the 60 Amp Ford alternator on my TR3A
> wouldn't keep up with headlights plus radiator fan, at idle.
>
> IOW the problem is not your charging system, it's the tach (assuming that
> the wiring is sound, etc.).  Any "reasonable" car electronic device should
> work down to at least 10v and up to at least 16v (and withstand pulses much
> higher than that).  (If memory serves, the tractor company I work for
> insists that our devices work properly from 7 volts to 30 volts, not sure
> what the impulse rating is.)
>
> BTW, Jim, you might look at a MSD tach adapter.  One of their units should
> make almost any tach work with a Crane XR700.
>
> -- Randall
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