[urq] 2 urqs on ebay fusebox differences

[Steve Eiche]

Steve,
After being up close and personal with '82,'83,'84, '85 and '90 ur quattro wiring, I can say that without a doubt, the later the car, the better the electrical system.  There were even notable improvements from '85 to '90.

As we know, the early cars with the Rabbit fusebox are the worst.  It isn't just because of the crappy old fuses.  The connectors and contacts themselves are of a poor design, and will often overheat and melt the housings. The fusebox itself is prone to failure of the internal soldered joints as well. The contacts themselves corrode due to the wrong or no protective plating leading to corrosion, high resistance and heat.  The wiring used on the early cars has an insulation jacket of a type of rubber that gets brittle with age and heat.  Then there are the well documented issues with the terminal 30 (battery) lines with multiple taps and series connections, etc., etc. etc.  I would hazard to guess that just about every early car has at least one melted contact at the fusebox, or term. 30 wire.

The '83.5s and '84s got the good welded fuseboxes, connectors and switches, but stayed with the poor quality wire.  In '85 they finally got the good PVC jacketed wiring.  I haven't had the harnesses from the '86-'89 cars in my hands, so I don't know when the changes were made, but there were a few that I can think of off the top of my head in the '90 RR harnesses that I have.  Most notably, a line was run from the battery to the fusebox in the rear body harness, in addition to the two that split off from the battery to start and alternator cable.  The fuel pump wire gauge was increased.  One connection was removed in the rear defogger wire and the gauge was increased.  Many of the higher current contacts were changed to the Junior Power Timer contacts with springs to ensure better contact at the fusebox, switches and relays.  There are a few others as well if I would really look.  I didn't get the main battery cable from the RR, so I don't know if it still had the dreaded splice.  Personally, I am using the main cable from a '91 200q as it no longer has the splice but rather separate cables all the way from the fuse block to the battery.  As a bonus, it is EXACTLY the same length as the ur quattro battery cable so it is a direct swap.

As for the '83s, there are a few things that you can do to make the wiring reliable, but IMO it still won't get to where the later cars are long term.  The big circuits to fix are the headlights, rear defogger, fuel pump, fan wiring, coil and power windows.  

BTW, if anyone is interested, I have an excellent '83 dash harness that I removed from my car.  It had been replaced before I got the car due to a harness meltdown (I have the original as well).

Steve


The right honorable Steven Buchholz wrote:

... hard to say for sure from my POV ... but keep in mind that there are
a *whole bunch* more '83 WX models than 84-86 ... couldn't that have a
little bit to do with the fewer complaints?  I'll poke around the wiring
diagrams in Bentley for comparisons, but I am skeptical that there were
any substantive wiring improvements associated with the under hood box
... and I know I remember posts from folks with BTDT on problems with
them too.  Note, I'm not claiming that the MB and beyond models were not
improved ... I'm specifically talking about the WX variant.  The main
improvement with the "under hood" box is that they moved to the bladed
fuses ... which isn't that bad an improvement.  

Has anyone sat the fusebox from the early WX with the later models?
I've always wondered if the interface connectors were comparable ... or
even compatible ...

... the sorts of things I'm referring to on the newer models ... wiring
looms in doors that have got the better part of 20 wires flexing (and
breaking) in the driver's door hinge ... internal "welded" grounding
points *inside* a wiring loom ... etc. etc. ... you'll never have to
worry about that sort of a problem in an urq!

Steve B
San Jose, CA (USA)