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Replacing wiring harnesses and Perils of working on cars

To: british-cars@hoosier
Subject: Replacing wiring harnesses and Perils of working on cars
From: augi@cbmvax.cbm.commodore.com (Joe Augenbraun)
Date: Tue, 3 Dec 91 11:13:33 EDT
> Date: Mon Dec 2 16:36:50 1991
> From: xgg2356@dcmdc.dla.mil (James Fuerstenberg)
> Subject: Re: MGTD wiring
> 
> Judy,
> 
> although not an "expert", based on my experience with old british wiring, if
> your wiring harness is original, it probably should be replaced.  It is not
> as daunting a task as it may appear, as the wiring on a TD is pretty simple.
> 
> Mark carefully what each wire comes off and mark from where it came.
> 
> and as they say in the  Haynes manuals, reassembly is the reverse of the 
>above.

I've replaced wiring harnesses in two XK120's, and have done major electrical
work in lots of british (and non-british) cars, and I must disagree with you
strongly.

I've run across exactly two bad wires the entire time that I've been working
on british cars.  I've found lots and lots of bad connectors, but only two
bad wires.  This does not include cases where the car had a fire with a melted
harness, or things that some former owner hacked in, etc.  I'm talking about
factory harness wires opening or shorting without being obviously melted or
cut.

If you have lots of intermittent electrical problems with an older british car
I would recommend replacing all of those Lucas inline connectors, the ones that
are a piece of steel covered with rubber.  Those things corrode badly within
a couple of years, and seem to be the cause of many british electrical problems.

If the car has been badly hacked by a previous owner, the thing that I've
always done is to try to reconnect the original harness, and then debug the
problem that the previous owner had hacked around.  Usually seems to be a bad
connector somewhere.  This can get quite confusing and time consuming, but
is something that you would have to do anyway with a new wiring harness.

If you must replace the wiring harness (if the car had a fire for instance),
the thing to do is to NOT disconnect the old harness at all, but to cut it
off at each connection.  This gives you a ready reference as to the color of
wire that the old harness had at every connection in the car.  You then
connect the new harness to each connection, discarding the old piece of wire
when each connection is made.

Maybe more common british cars are better, but the two XK120 harnesses that
I did were nightmares.  The harnesses came with NO documentation, and were
not a close match to the original harnesses both in terms of wire colors, and
lengths.  In some cases even the bundling of the wires was different (like the
wire to the fuel pump in the original harness was part of the body harness,
in the replacement harness it was its own wire).  Some wires were way too long,
some were too short, and it just generally was no fun.  These were harnesses
that came from Rhode Island Wiring, or something like that.

---------------

I thought I would also add my scary experience to the safety discussion.  I was
disasembling an early XKE brake caliper, and pressed the piston in and got old
brake fluid squirted right into my eye!  Luckily I was near a sink and washed
it out right away, but the experience made me much more careful around
hydraulics.  It was a hazard that I had never even considered.

                                                Joe



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