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Re: Ignition Warning Light on with new alternator

To: sosnaenergyconsulting <sosnaenergyconsulting@cox.net>
Subject: Re: Ignition Warning Light on with new alternator
From: Theo Smit <tsmit@shaw.ca>
Date: Thu, 12 Sep 2002 21:38:58 -0600
I'll take a swing at it.

First off: Read Larry's post carefully: One wire to the battery/starter 
solenoid,
and another wire to the light. The one-wire alternator has TWO wires. My Toyota
alternator has three: the output wire (big bolt-on post) and two spade-lug
connections, one for the ignition and the other for the light. The "one-wire"
alternator combines the function of the last two connections, and Steve L's
description of its operation is pretty much correct: When the ignition is on but
the engine isn't running, the alternator doesn't put out any current, and its
internal regulator pulls some current from the 'light' connection to turn it on.
When the engine is running the alt output is above some threshold, and the
internal regulator turns off its current switch for the 'light' output. When the
ignition is off the voltage at the light is zero, and the alternator's regulator
takes that as a cue to do nothing. If your charge light is on when the ignition
is off then either the light is wired to the wrong side of the switch, or there
is some internal fault with the alternator that is allowing the current flow in
the wrong direction (some older cars had the diode Steve and Tim Ronak referred
to on the instrument panel circuitry but this newfangled alternator shouldn't
need it).

So we should have

12V ---> ignition switch---> (run position) -->light--->alternator 'red' wire 
-->
alternator.

Clear as mud? Let me know - I can try and draw you a schematic and email it.

Theo

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