Firstfives.org

Wanted to share that I upgraded my fuse box to blade fuses after looking for a solution to overheating fuses.

https://www.mye28.com/viewtopic.php?t=156216

You probably need electrical experience before attempting this. I took plenty of photos. It was very zen spending an afternoon reconnecting each line one by one and double checking everything.

Things I learnt:

IMPORTANT - Our solid green coil line is NOT FUSED. Maybe there's a fusible link somewhere but mine was directly connected to the ign line on the input side of fuel pump fuse and I've read other people discovering this. I moved it to the fused side of the 'fuel pump' fuse. My Motronic setup has a separate fuel pump fuse so that is now the 'coil' fuse, but a regular L-Jet e12 could bump the fuse up to say 15 amps and run both.
I had to cut a bunch of additional slots, the plastic is soft enough a knife will do it. You also need to carefully cut the guide paper.
Some of the links were soldered, I converted them to spade terminals.
The 8A fuses are not enough for our 4x high beams, the fuses blew immediately. If you are running two "8 amp" fuses then they are allowing a lot more current through, which shows how sketchy the bullet fuses are.
I also modified the US market 'disable low beam when hi beams are on' setup. There's a diode that is grounded when hi beams are off, but is + with high beams, which cuts power to the low beam relay. I removed that then rewired the low beams to be always grounded, then cut disconnected the outer high beam line, so I now have the Euro style hi-beam flash while my low beams stay on.

Nice work, looks good!

A FWIW, on Mye28.com there's a lengthy thread about the conversion and some of the fallout. One of the upshots is that the new ATO blade fuses are much more accurate, precise and less forgiving of an overload. Seems the old GMB "bullet" fuses will blow sometime, eventually, under some load, but are not very accurate about the real fuse rating. So if a fuse is even close to borderline, it can start blowing and be a routine problem. While I would hesitate to recommend "fusing up" on those problem children, it is probably a fairly safe and pragmatic solution. After of course researching and what the load should be and is, before just throwing a bigger fuse in.

Thanks! One of the other issues I had with the bullet fuses - not sure if others find this - is the new ones are plastic not ceramic, and also are so poorly made the wire tends to just fall off. So it feels like they're even less accurate than the old ceramic ones.
Something I forgot to mention, the "Holy Grail labs" sockets also support mini blade fuses and I think micro blade fuses too which is useful because most of our daily drivers will already use that fuse type so in a pinch we'll have spares.

Oh, the plastic fuses are absolute junk, especially in 16 and 25A applications. Last I knew ceramic were still available, you just had to look for them. The glass fuses aren't really much better, they don't blow, but the solder in them that holds the fuse link to the end melts with heat. Again, in higher amp applications. So it seems while the blade fuse retrofit is the real winner, short of that is just the original 50s (?) ceramic fuses.

I was able to source ceramic bullets during the last few years, possibly from Walloth Nesch because they're shown at $1.69 each.

Lock, are the green LEDs on the Holy Grail board illuminated when the fuse is active? A handy feature, that.

528i-1981 wrote: ↑Fri Apr 14, 2023 7:39 am I was able to source ceramic bullets during the last few years, possibly from Walloth Nesch because they're shown at $1.69 each.

Lock, are the green LEDs on the Holy Grail board illuminated when the fuse is active? A handy feature, that.

Hey Eric, the LEDs are illuminated green when the circuit is powered, and go red when a fuse blows as I found when I tried the high-beams. But thoughtfully they included a tiny toggle switch to turn the lights on/off as well - makes sense because a couple of circuits are battery/always powered.

The wires are so tightly packed in the box, to make re-assembly easier it I removed all of the diagnostic socket wires. No noticeable change to the electrical system, but everything stays cool in there and they should have much better control of overcurrent situations.