On Sat, 30 Jul 2005 03:43:17 -0700, firstname.lastname@example.org
electrons to form:
> So you're thinking the alternator could be at fault? I'll go to Hammons
> Auto Parts first thing Monday (where I bought it) and let them test it.
> Grrr.. what a pain in the ass =(.
An alternator works by creating a rotating magnetic
field which cuts across a set of wire windings.
As Mr. Faraday and Mr. Maxwell told us, a changing magnetic
field intersecting ith a wire creates a current in the wire.
Since the field is rotating, the current alternates between
positive and negative and thus creats alternating current (AC).
Strategically placed diodes forces the current to go in the same
direction, thus creating direct current (DC).
The rotating field is created as DC current from the battery flows
through slip rings to a field winding on a rotor
that is spun by the belt pulley.
Some time ago I disassembled the alt. on my
Torino and installed a "hi-output" kit.. new brushes, different
stator winding, and some bigger diodes. If I am at a slow idle (stopped
at a stop light whilst still in drive), the alternator output will drop
enough that the voltmeter drops below 13 volts. The regulator leaks
enough current through the ALT light to turn it on just barely in that
case. Goosing the throttle makes it go back to normal.
The regulator is trying to put enough field current through the
rotor to keep the voltage up at low RPM. When it hits the maximum
current, the output voltage drops and the light comes on. The
OEM style regulator was only able to vary the field current
discretely, it had a relay inside that basically turn the field
on and off to maintain the output voltage. An electronic regulator
(which I have now) can vary it across the range of adjustment.
Guess what, 35 years later, alternators still work the same way,
except now the regulator is built into the unit.
I would take the unit back and have it tested. I haven't ever
had too much luck with generic auto parts stores alternators,
they don't really last very long. I would try NAPA.
Also, it's possible that they didn't hook it up right....
David M (dmacchiarolo)
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