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Re: New Alternator Question

To: british-cars@autox.team.net
Subject: Re: New Alternator Question
From: "Andrew C. Green" <acg@hermes.dlogics.com>
Date: Tue, 27 Oct 1992 14:12:43 CST
Don Mathis (tdm@akguc.att.com) writes:
> The turn signal no longer flashes.  Also when I turn the turn signal on
> the right brake light also comes on. I assume I have mis-re-wired
> it.

I confess I don't know the taillight setup on your particular car, but
the symptom you describe is usually caused by a bad ground. The current
leaving the bulb finds its ground connection blocked, and doubles back
through the other filaments sharing the same ground connection.

In this scenario, the symptoms change when you test the brake/turn-signal 
while the taillights are ON. When they're on, the taillight that glowed
unexpectedly last time now goes OUT when you flip on the turn signal. This
is because the light finds that it has voltage not only on its supply wire, 
but also coming in from the ground side, the doubled-back current flow
from another filament sharing the same bad ground. The two voltages cancel 
each other, and the bulb goes out.

> The left headlight comes on but is very dim as is the small driving light
> below it.  I assume I have a poor ground.  

Yup. The bad ground effectively serves to link the two lights in series, and
they both glow dimly. I venture to guess that if you switched on the driving
light itself, it and the headlight would both go out.

Andrew C. Green
Datalogics, Inc.      Internet: acg@dlogics.com
441 W. Huron          UUCP: ..!uunet!dlogics!acg
Chicago, IL  60610    FAX: (312) 266-4473


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