In about 1984 the 4k/coupe Audis finally abandoned the old VW style fusebox under the dash and moved it under the hood, behind the firewall and in front of the windsheild. These new fuse boxes have several advantages: No more grovelling in the mud on your knees to check fuses. Better internal construction increasing MTBF.
Blade type fuses - better contact area and easier to obtain than the quaint "German" ones. Large, spade connections to the wiring harness instead of little round pins. Fewer problems with moisture penetration - one little windsheild leak can ruin one of the old boxes. Easier access (believe it or not!) to the wiring harness to modify and repair. The only problem with this modification is a big one. The wiring harnesses not only use different shaped pins, in a different style connection block, they are just plain different. The cars have different engine operating systems and some of the same function wires are different colors. So there are two competing philosophies of how to get around this - swap the harnesses as well, or cut and splice all the wires. To be brief, I think the harness swap makes the most sense on a stripped car being rebuilt from the ground up. In fact on a ground up restoration I think one would be amiss not to swap the fuseboxes. The cut and splice method is best if this is the only modification being performed at the time. The following is some theoretical and practical information on the job. Having dismantled a spare 82 fuse box and hacked apart a handful of 84 - 87.5 cars, I have some definite opinions about various aspects of this job. What piqued my desire to do it was the idea of pulling all my fuses this spring and cleaning the contacts and replaing them with glass type German fuses. The thought of crawling around on my knees with the door sill digging into my side and a work light blinding me every few minutes, did not appeal to me. The thought of having my fuses and most relays be accessible while standing, and getting rid of the clunky internals of the old box, started to get very appealing. To say nothing of the fact that the blade type fuses are readily available almost everywhere, including other people's glove compartments, this job has pretty much got a green light from me at this point. Another point in its favor is that it is pretty much a no cost modification (I already have several fuseboxes to choose from). The only items to be consumed are: a bit of solder and a lot (about eight feet) of heat shrink tubing, a lot of patience (I'm old, I have more patience than I need!), and some (a lot of?) time. As has been pointed out on Audifans, I quote, "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." My reply to this is: 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 mounted in the fuse box. I already have a file I created which lists every fuse box input and output, it's function, and the color and gauge of wire attached to it. All I have to do is the same thing for whatever my donor vehicle happens to be, and match the circuits betwen the two files. This may sound like a lot of work, and I suppose it is, but it mostly involves sitting at the computer, for as long as I like at a time. It won't entail preventing me from driving my car and it won't get me dirty or scrape my knuckles. 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 the list. If one chooses to be very meticulous, systems could be wired as groups and tested along the way. Some new style relays would be required - the newer fuel pump relay has a different pinout, some of the newer X relays are 70 amp devices with larger pins, etc. These are usually available from the donor vehicle, so pay attention to them. There is also the opportunity to run new wires to the alternator and battery. For a while I have had a bunch of doohickeys saved up for a "ground upgrade" project, consisting of some new heavy wires for the battery, a jumper to the alternator case, etc. While the fuse box is out, it would make sense to do the other half of this project as well. My 82 has a triangle of wires - one 8 gauge wire form the alternator to the battery and the fusebox, and one between the fuse box and the battery. It would be nice to replace these with new 6, or even 4, gauge wires. I'm not arguing against swapping harnesses in general, but from what I have seen I could probably swap the box by the splicing method 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 doing a serious rebuild finds themself in anyway (building 4kqt's, etc.). Getting those harnesses out alive and putting 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! This is very likely, in fact. A lot of these car's secondary connections use different styles of plugs and jacks in the later years; also the switch from K-Jetronic to CIS-E took place at the same time as the fuse box change. This means the wires to all the cars auxiliary systems (headlights, windsheild stuff, etc etc), will have to be reterminated anyway. The one harness that might make real sense to swap is the dashboard switch wiring. The fuse box project would dovetail very nicely with a dashboard upgrade, and swapping this harness will save a lot of splicing to accomodate the newer style switches. In fact, to anyone considering one of these jobs at this point, I would recommend doing both, due to the large dismantling time savings, and easier access with the whole dashboard out of the way. Another point that might be useful to be aware of, 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 vehicle and patch it into yours. That's all for now. If and when I get around to doing this you can certainly expect some serious work files and photos to turn up here! |
