"Jim Thompson" wrote in
message ...

Don't buy GM products and it'll never be an issue ;-) Magnetized
rotors and headlights-always-on... so GM could save one piece of wire
from ignition switch to regulator.

...Jim Thompson

Only time this was ever a problem was on the 1 wire marine alternator on a
friends boat (Ford 351M). Because everything has to be flame arrested so a
spark in the engine compartment won't ignite any fumes, they often use only
the rectified output as a single terminal connected to the battery. The
idiot light connection and battery sense are tied together inside the case.
Problem was that you practically had to red-line the engine to get the
alternator to start outputting. I finally gave up and put another
feedthrough in the case for the idiot lamp. Connected it conventionally
through a pilot lamp (and diode) to the + igniiton coil (switched battery).
From then on it would generate at idle.
Adding the diode is an old trick dating back to the '70 when 'engine run
on' was a big problem. Jim knows this since he designed automobile
regulators. Diode keeps the idiot light from turning on when you shut down
the engine. Without it, current flows through the idiot lamp from the field
supply to the ignition coil. Gives just enough spark to make the engine keep
running (poorly) or even backwards depending on how much basic spark advance
there was.