[alfa] Alternator explanation needed..

[AlfaNeely@xxxxxxx]

In a message dated 7/25/2004 12:26:57 AM Central Daylight Time, 
owner-alfa-digest@domain.elided writes:
Date: Sun, 25 Jul 2004 01:21:25 -0400
From: "Brian Shorey" <bshorey@domain.elided>
Subject: [alfa] Alternator explanation needed..

Hey folks,

I'm trying to help a friend get a car running for the convention, and I need
an explanation of how an alternator works..  We're wasting too much time
staring at wiring, and not making fast enough progress.

We finally got the car running today, but when trying to determine if the
alternator is charging we came across some puzzling data.  First, an
explanation of what we're working with, then the data we're observing.

The car is a late 60's Giulia Super.  The dash and gauges are a hybrid of
stock and aftermarket (stock gauges, aftermarket ignition switch).  The
engine is a Spica injected 2 liter.  There is no wiring harness (we're
making it up as we go), and the fuse box is some aftermarket thing.

To confuse things even more, we didn't have an external voltage regulator,
so we tossed the alternator that came with the 2 liter and bolted up a
Milano alternator.

The Milano alternator has one stud, to which we connect to the hot lead on
the solenoid.  Then it has only one other lead, to which we run a green wire
to ???

It looks like the green wire should be connected to an alternator warning
lamp.  Ok..

If we don't connect the green wire to anything, the car starts and runs
fine, and stops when we turn off the ignition switch.  However, to test the
alternator, I tried disconnecting the battery with the car running and it
stalled immediately.

However, if I apply 12v to that green wire, the car will run with the
battery disconnected.  BUT, if I turn off the ignition, it won't stop
running until I disconnect the green wire.

I'm not sure I understand how this should be working, what I need to connect
it to, etc.  The best I can see is on a wiring diagram for a late 70's Spica
Spider, which shows the green lead connected to the alternator warning lamp,
and the other side of the lamp connected to a switched ignition lead?

Thanks in advance for any insight anybody can provide.

bs
---------------------------------

    It is my understanding that the green wire supplies 12 volts to the field 
windings.  That is, the electromagnets that create the magnetic field are 
operated by the 12 volts.  On race cars, the master kill switch is wired to 
disconnect the battery and the green wire.  Cutting the current in the green wire 
and disconnecting the battery will kill the engine.
    Disconnecting the battery without killing the field power will not kill 
the engine.  The engine will continue to run on alternator current.  Plus the 
alternator has no reference of 12 volts and the voltage can spike turning 
various and sundry electrical components to toast.
    Or at least that is the way I understand it.

    And as New Hampshire Convention Chair, how do you have time this close to 
convention to be messing with Alfas?


Ciao,
Russ Neely
Oklahoma City
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