Re: fuse box upgrade

[Huw Powell <human@nh.ultranet.com>]

> Actually there are a lot of changes to the fuse/relay panel. The obvious
> external changes, blade style fuses and spade type connectors for the
> harness. There are also significant changes to the internals which results
> in a much mode durable board. The old style boards were several circiut
> boards press fit together with the connector pins making a mechanical
> connection from circuit to circuit without any solder joints. They were very
> susceptible to corrosion damage and pins becoming loose.

Having dismantled a spare 82 fuse box I agree emphatically.  the typical
circuit has 6-8 mechanical connections of a not very convincing design
in the box.  My radiator fan circuit melted it's little connector pin
that goes to the fuse contact and I had to rewire it.  The pin going to
the dash light/parking light circuit melted and had to be bypassed...

> an upgrade. I think you could spend an enormous amount of time just
> determining how to graft the old harnesses to the new board, the wiring is
> quite different.

Yes, but... armed with both circuit diagrams, one can make a list of
what every wire going to the old fuse box serves.  then diagram the new
fuse box connections, to determine where the old wires should go.  there
will be some (in my case) simplifications - eg the fuel pump relay on
the 82 is outboard, on an underhood box it is in the fuse box.

Equipped with this list, which should correlate every old wire with an
appropriate new connection, one can just  cut the hole in the plenum and
start "following instructions" by splicing every wire on your list.  if
one chose to be very meticulous, systems could be wired as groups and
tested along the way.

Some new style relays would be required, as I have mentioned, the newer
fuel pump relay has a different pinout, the newer X relay has the huge
pins, etc.

There is also the opportunity to run new wires to the alternator and
battery (larger, more flexible...).

I'm not arguing against swapping harnesses in general, but from what I
have seen I could probably swap the box by splicing in a long weekend. 
To swap harnesses would require massive dismantling of not one but two
cars - which of course is often the position the fuse box swapper finds
themself in anyway (building 4kqt's, etc.).  getting those harnesses out
alive and puting them back neatly is a big job.  Plus, depending on the
models and vintages of the cars (donor, donee) the harnesses won't fit
at the other end anyway!

The one harnes that might make serious sense to swap is the dash switch
one, if one is swapping tot he newer dashboard at the same time that
will save some splicing.

Another point that might be useful, is that the cutout in the plenum has
a flange around it, which probably acts as a last ditch defense against
water infiltration so it might make sense to either duplicate it somehow
or to cut out the sheet metal from the donor and patch it into the donee
vehicle.

-- 
Huw Powell

http://www.thebook.com/human-speakers

82 Audi Coupe; 85 Coupe GT
http://www.nh.ultranet.com/~human