Message text written by Randall Young
>> Will an alternator start without this "idiot" light? Yes it will.
Here's
> some empirical evidence: On day, as an experiment, I
> disconnected the wire
> to the charge light on my TR6 (which had sat idle for at least a week)
and
> started it up. I slowly increased the engine speed until the charging
> circuit kicked in (as indicated on my ammeter). The alternator started
> working at about 1700 RPM. With the light connected it usually
> kicks in at
> 1200.
This seems to vary with the alternator (possibly depends on the
characteristics of the regulator, or even on the material used in the
rotor), but the old Ford unit I used on my TR3A would not self-start even
at
5000 rpm. With only the original ign lamp, it wouldn't reliably start
below
about 3000 rpm.
<
This must be a peculiarity of the alternator, not inherent in the
"alternator" configuration. It is basically the same thing as a dynamo,
only inside out.
Perhaps a note about how speed effects generators (alternators, too). The
output voltage is proportional to speed. Infact the primary function of
the regulator is to compensate for speed variations. It important that the
residual magnetism be low enough to ensure that the output voltage due to
residual is not greater than system voltage (14.2 V) at maximum speed else
you have a potential overcharge situation. Perhaps Ford used a smaller
pulley than you used and designed to prevent an overcharge at a much higher
alternator speed than you were achieving at 5000 rpm. But I am
speculating.
Cheers
Dave
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