[DML] Re: How does the Alternator light work???

["David Teitelbaum" <jtrealty@xxxxxxxxxxxxx>]

The wire from the bulb to the alternator is called the "sense" wire.
It's primary purpose is to tell the alternator when the ignition key
is on so it knows to excite the field coil which makes the alternator
produce electric. John is right when he says it also reverses the
voltage to make the light go out. In fact that is why the light lights
when the alternator is NOT producing electric so you know there is a
problem with the charging system (it's NOT producing electric!). Of
course this assumes the bulb is not burnt out, the wiring is still
good, and the regulator is still working a little bit! Another tidbit,
the alternator produces 3 phase A/C. The diodes rectify it to
fluctuating DC and the battery filters out the harmonics. One of the
reasons you should never disconnect the battery with the motor
running. The voltage spikes and harmonics can damage sensitive
electrical components. When you start the motor and turn the key to
"ON", just before you hit the starter, you need to see the alternator
light. If it doesn't light then the alterantor won't be charging and
you won't have a warning light to tell you!
David Teitelbaum
vin 10757



--- In dmcnews@xxxxxxxxxxxxxxx, "David Rucker" <davidrucker11387@...>
wrote:
>
> Those same thoughts crossed my mind as well about how it works. I
havent had
> the time to go over the schematics yet but i do plan to do so.
However if
> the bulb did work how you explained, which to me seems the most
logical and
> efficent way to check something like that. However if it did work
that way
> the alternator should still work if the bulb goes out. But when the bulb
> does go out the alternator and the rest of the charging system
starts acting
> up. Just my thoughts.
> 
> Dave
> 6410
> 
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