[Vwdiesel] Wiring Issues Behind Fuse Block on '84 Rabbit

[Bryan K Walton]

(Long email warning) I know most of you are going to laugh at me for 
caring to fix this, but here goes . . .

In my '84 Rabbit, I've got a problem with upshift light.  I've been
troubleshooting this for a while, slowly eliminating various things
that could be my problem.  The problem I'm having is that the light
flickers on and off.  Sometimes it comes on at the correct RPM level,
sometimes it doesn't.  Eventually, it always comes on in top gear --
something that shouldn't happen.

1. I've replaced the switch on the tranny with a brand new switch. 
According to the Bentley manual, it works exactly as it should.  Plus,
my backup lights work fine.

2. There are two other switches that affect the upshift light.  One is
the idle switch and the other is the 70% of maximum throttle switch. 
Those are in good condition and work as described by the Bentley
manual.

3. The W terminal on my alternator works correctly.  I was the guy
who recently solved my oil pressure warning light problem.  During my
troubleshooting of that system, I learned a lot about the W terminal. 
I ended up replacing the oil pressure control unit and the W terminal
now correctly communicates with the OPCU.  There is only one wire
coming off of the W terminal.  Somewhere, I'm assuming behind the fuse
box, this wire splits and goes to both the OPCU and the upshift
light relay. 

4. So at this point, I assumed that the problem was my upshift light
control unit.  I bought a replacement unit and put it in.  But with
the new upshift light relay, the upshift light stays on continuously.
Hmmmm, something isn't right with one or both of the relays.

5. I put the old relay back in.  (I'd rather have the upshift light
working part of the time, than have it lit up all of the time).  Back
to the Bentley, it says that with the engine running, I should be
getting current to the corresponding terminal on the upshift light
relay at the fuse box.  I don't -- or at least not when I checked it
this one time.

So now I'm under the assumption that the problem is either a short
in a wire somewhere, or in the connection between the wire and the
back of the fuse box.  Shooting in the dark here, I'm going under the
assumption that some water has seeped in there sometime in the past
and done some corrosion.  I'd like to take the fuse box off and look
around back there.  Perhaps clean some terminals.  What am I going to
find behind the fuse box?  I'm very afraid of pulling the fuse box out
and in doing so, accidentally loosing connections to other wires.  Can
somebody describe for me what I'm going to see back there?  How do the
wires connect to the fuse box?  Can they easily be removed and
reinserted?

Thanks!
Bryan