I was troubleshooting the batteries, cables, fuses, etc. because my panel was showing 8V on both batteries. However, I was measuring the batteries directly and they were showing 12.91 - 13.1V. Not the batteries. I did find one 100A fuse that was showing a resistance of 267 Ohms. Took the time and replaced the old Buss fuses with modern spade types. Yet, my panel was insisting on 8V for the battery banks. Just for giggles, I opened up the DC panel. Yep, the meter is showing what the panel is doing. Took my meter and paralleled the 12V buses and got 0V. However, when I did the same thing on the ground side...4V shows up. It appears the panel ground is bad. Followed to the next tie point. Don't see anything injecting a signal, but the wire is corroded. Will cut it back and put it to a good, strong ground bus that has the wire to handle the job. Strange things happen in the electrical world. Glad I looked behind the panel. My 12V bus is about to be healthy again. This is an old technique for finding when starter cables to battery go bad or is undersized. Hope this helps somebody else down the waterway. Rick