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Re: Weirdo electrical problem

To: "Telewest \(PH\)" <paul.hunt1@blueyonder.co.uk>
Subject: Re: Weirdo electrical problem
From: Tab Julius <tab@penworks.com>
Date: Tue, 20 Aug 2002 09:49:08 -0400
Thanks - this was a big help!  The sun's coming out, the engine is nice and 
cool from sitting all night - I'm going to start taking a closer 
look.  Will letcha know what I find.

- Tab


At 05:22 AM 8/20/02, Telewest \(PH\) wrote:
> > I've run into a weird electrical problem (aren't they all, though?).
> >
> > I have a '78 B - the other day while driving my stereo cut out for a
>second
> > then came back on.  It happened once or twice thereafter.  I figured I
>just
> > had a loose wire.
> >
> > I then noticed that when the stereo is off, so are the following:
> >
> > - Horn doesn't work
> > - Cigarette lighter socket has no power
> > - Convenience interior light (that little one about the heater controls)
>is off
>
>All off the purple circuit (fused, always hot), bottom one in the main
>fusebox.  Check the voltage on the brown feed to it and the purple from it.
>
> > Further, the turn signal is acting weird - it stays on longer than usual
> > then will speed up, but is never quite at the normal speed.
>
>Green circuit (fused ignition), 2nd one up.  Any slightly variations in the
>12v supply to the turn flasher or the switch and lights from it will cause
>this.  However this is going to be the hardest to track down so leave it
>until last.
>
> > Finally, though I will test tomorrow - the temp gauge got REAL high -
> > touching the red - while sitting in traffic, leading me to suspect the
> > radiator fan wasn't kicking in, but I wasn't in a position to check just
>yet.
>
>Comes off the ignition relay.  If that had failed the engine would stop, but
>check its own in-line fuse etc by linking the connections to the thermo
>switch while the ignition is on.
>
> > Things that seem unaffected:
> > Headlights
>
>Brown (unfused always hot)
>
> > Dashboard/Instrument lights
>
>Ditto
>
> > Overdrive switch (it's electric)
>
>White (unfused ignition) from the ignition switch which is fed by a brown.
>(Aren't they all?)
>
> > Wipers
>
>Green circuit again, but a different branch from the fusebox (there are
>many) to the turn signals.
>
> > If the things that were broken were always dead, I'd just go looking for a
> > short,
>
>Shorts blow fuses and burn wiring, it's almost certainly one or more
>open-circuits.
>
> > but because it all works for the first 10 to 60 seconds, then it
> > dies, I'm suspecting an electrical component is flaking out, but don't
>know
> > who the culprit might be.  In the morning, after it sits all night, I'll
> > see if it stays on for more than 60 seconds.  In the meantime, I'm hoping
> > maybe someone here with a better understanding of All Things Lucas would
>be
> > able to point me in the right direction.
>
>Looks like you have several problems, just pick on one at a time and track
>that down, don't go looking for a magic bullet.  Electrical connections can
>be loose and slightly high resistance then go higher resistance and fail
>altogether as they heat up due to the initial slightly high resistance.  I
>don't see one 'component' being responsible, with the possible exception of
>multiple bad connections in/to the fusebox.

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