Hi Terry:Okay, it’s official: you have now properly terrified me! In 1989 and 90 I had a ‘74 Manta with over 200k miles that I thought was waaaaay overdue for the wrecking yard. That was before I had any interest in Opels and I didn’t have the resources to restore a car, even if I’d wanted to. It just got me from point A to point B (usually). It had a lot of electrical issues, e.g. the fuel gauge, turn signals, and many other functions didn’t work, nor did the speedo and some other mechanical functions. I decided to buy a complete harness from Opels Unlimited (so it may not have even been completely good) and change mine out. A buddy and I took 6 to 8 hours to do it, but once it was done, it had the exact same problems still! I was working as an electronics technician at the time, but I knew even less about automotive electrical than I know now, if you can believe that’s possible, and thinking about it now, I didn’t think to replace, or even check, any of the ground connections. 🤦♂️
I have the time and ability to replace brown wires, if I know where to find them all, and I even have a couple of new spools of brown wire. I even have a crimper, and I’m not afraid to use it! It’s just going to be uncomfortable as the weather warms and it gets to be 250° in my garage at night. 🥵 I replaced the ground wire on my left headlight because the light was dimmer than the other. It fixed the problem for a few weeks, but it’s dim again.
As far as the interior gauges and functions go, if one or more of them are shorted, shouldn’t fuses be blowing, now that I’ve replaced all of the 25A fuses with ones that are correct? The only “gauge” that’s not functioning properly is the clock, and I think all of us are familiar with that particular nuisance.
I have at least one wire (the red alt B+ wire, in fact) that has some cracks on a section of insulation, but the wire is good. Nevertheless, I don’t have a problem with running a new wire or twenty.
By the way, my wiper issue is entirely mechanical, and I’ve had it from the beginning. I changed out the motor and resolved it, except I can’t find a passenger side wiper arm with a mounting hole that’s not warbled out with the fluting worn away. It’s okay, though. It doesn’t rain much in the desert for some reason (we had 260 days last year with no precipitation), and my occasional passengers don’t need to see when it does. 😎
Have you check voltage drop on your ground locations? Have you used "star washers" on you ground posts/bolts? Good luck!!