The gauges in the instrument panel of my 1984 BMW 318i are, with the exception of the speedometer, all dead. I checked fuse #10 in the fuse box, and yep, this mighty 30 amp fuse was blown. That would explain the dead gauges. I replaced the fuse and as soon as I turned the ignition key to “on” the fuse blew again.
So, the issue is a short-circuit downstream of the fuse.
I looked at the documentation, and it shows how the wiring from the fuse goes along three separate wires, two of them being green-and-white and attached to the instrument panel, and the third wire going … well, I haven’t as yet been able to figure that out.
This makes the instrument panel the prime suspect. I removed it, installed a fresh fuse, turned on the ignition key … and the fuse blew again.
So, now I can conclude that the issue is a short-circuit between the fuse and the third wire, wherever that goes, or in the wiring or connectors for the two green-and-white wires. I was hoping for an easy fix, but … no such luck.
The bottom of the fuse box has always seemed intimidating to me, but tonight I dealt with it. I disconnected the battery, and I took off the clear fuse box lid, and saw a Philips screw. I removed it. I tried to lift the top of the fuse box, but it didn’t budge. I removed the two relays close to the firewall, and found a second Philips screw, sort of diagonally opposite the first one. I removed it, and then I was able to lift the top part of the fuse box off. Yay!
Next to the inboard row of fuses, including the #10 fuse in which I’m so interested, was a set of four black plastic catches. I slipped these, and it loosened a piece of plastic whose purpose perplexed me, and aside from that it didn’t seem to make a difference.
So, I peered underneath and saw a couple of green-and-white wires, wound together and coming out of the area where fuse #10 would be. Interestingly, although both wires were green-and-white, they had different styles so it was possible to tell them apart. Clever, these BMW engineers.
I traced the wiring and saw the two green-and-white wires vanish into a massive wiring harness that exited the base of the fuse box. I loosened an 8mm bolt at the front of the fuse box base, and was able to lift the base up enough to see the wiring harness go through a hole in the firewall. I opened the driver door and peered underneath the dashboard area, and I could see the area where the wiring harness entered the passenger compartment. I could even make out the green-and-white wires. So, now I get to trace these, inside the car.
I put the fuse box components back the way they were, except that the black plastic piece didn’t fit as snugly as before. I hope that won’t cause problems. I reconnected the battery, then started the car to make sure it would start and run. It did. Yay!