Member @Galahad is building a blade-style fuse retrofit kit for E28s. He asked me to help him test/debug his solution and I couldn't resist. I absolutely HATE the bullet fuse design and have been contemplating how to convert our cars to modern blade-style fuses since the beginning of time. I actually bought a late-E24 new fuse box for Minerva and had all intentions of figuring out how to modify the wiring harness to make it work. I decided to wait until after the car was settled before doing that though.
It was a mistake choosing to use Minerva as @Galahad's test case though. I should have gone with either Vlad or Maytag...because they are US cars with US fuse boxes. @Galahad had not considered the Euro differences in his design, and I didn't understand those differences myself. I choose Minerva because it was the car that was in the garage when I decided to dive in. In the end, however, my trials and tribulations getting the kit to work in Minerva will pay off for everyone else because we, collectively, now have tons more details on how both the US and Euro boxes are wired.
See my thread documenting all of that here: viewtopic.php?f=3&t=155587
I've been inside the E28 fuse box before. On one of my cars, I think Maytag, I did some surgery at some point... I dont' remember why. Anyhoo, I knew enough to take tons of pictures as I pulled it apart and I'm glad I did. All the pics were invaluable in documenting it all and final reassembly. It started here:
If you click on those photos, you'll go to my Flickr album and you can scroll through the rest. I've tagged those photos with "BMW E28 Euro Fuse Box Wiring" so they'll show up in Bing searches for others. If you searched for such a thing yesterday you got nothing useful.
@Galahad's concept is very slick. Brilliant even. The idea is a circuit board that replaces the bullet-style fuse holders in the original box. The board includes blade-style sockets for all 17 of the original E28 fuses as well as sockets for 4 spares. LEDs are provided that show status of the the fuses (off: no power, green: power and good, red: power and missing or blown). He's engineered the board such that it supports the right amount of current.
To install you need to irreversibly modify your original fuse box. For Minerva I had ALSO ordered a brand new-euro fuse box way back that we ended up not using because the box that was on the donor chassis was fine. I choose to modify the new one and then swap it into the car. Using a screwdriver and a pair of needle-nose pliers I pulled all of the bullet-fuse holders out through the top. This is a one-way door...
Once they are removed, the new circuit board just slides into place providing all the same pins. Apparently, on early fuse boxes, the leads that attach to the relays on the underside are soldiered to the pins, so retrofitting will be a bit more work.
Once I got everything plugged back in I quickly discovered something was wrong. Like the idiot I am I never really considered the US and Euro boxes would be different. They are. The difference that matters to this conversion has to do with the high-beams. On US cars fuse 7 is the right high-beam and fuse 8 is the left. The inputs to those 8A fuses is the same YL 2.5 wire from the high-beam relay. The input-side (top) of the bullet fuse holder is bridged between 7 & 8.
On Euro cars Fuse 7 is 16A and carries both the right & left high beam. It is powered by the YL 2.5 wire from the high-beam relay. Fuse 8 is 8A and is for things other than high-beams and gets its power from the same VI 2.5 wire that powers fuse 11. The fuses have independent inputs:
In my case, my stupidity (and @galahad's not knowing about Euro differences) meant that I had both the YL 2.5 and VI 2.5 wires plugged into the same bridged input between Fuse 7 & 8.
It took me far longer to figure all this out because I had (stupidly) put a US fuse box cover on the car. This led me to continue to believe Fuse 7 and Fuse 8 were for high-beams. Eventually, I figured it all out and realized the fix was easy: Cut the traces on @galahad's circuit board between fuse 7 * 7. We've discussed this and in his final design he will make the bridge between those fuses something that can more easily be modified so his design can work for both styles. I determined there are no other deep differences between the US & Euro boxes. Although some stuff does plug into different places, from the POV of the retrofit kit all will work.
The other interesting thing about @galahad's design is built-in diagnostics LEDs for each fuse. HIs prototype has them working at all times, even when the car is off. This means that fuses 4, 5, & 17 are lit green even when the car is off. I don't like this because these cars don't need any more parasitic drain than they already have. I choose to put a little switch in place to control the ground for the LED circuit. @galahad says he's going to make it so they only work when the car is in ACC or RUN in his final design, which I'm cool with.
I've ordered a new Euro (UK English) cover from Blunt.
I was able to clean up some of the engine bay wiring around the fuse box since I had it all out too.
And, of course, spares:
This is an amazing mod and I'm grateful to @galahad for creating it. He indicates it will be a few months before he has the time to build the final versions. I'm sure he'll create a thread here when he's ready.
While I was in there, I fixed the fact that 425 didn't hook up the city lights properly. They didn't realize how the Euro lights went together and thus modified the euro harness to plug directly to the backs of the bulbs, without using the intermediary connector & boot. I had to undo all this and wire it up as it was from the factory. The city light bulbs weren't even installed!
But now city lights work correctly!