For the most part, my 1987 Excella has not had 12-volt issues. About 2 years ago my batteries had failed and, as I was in the Las Vegas area, I contacted Interstate of Las Vegas. I drove over to their place and a couple of their guys installed the new batteries. During the installation, for a split second, the negative cable brushed by the positive post and there was a bit of a flash. Everything worked fine afterwards and I thought nothing of it.
Fast forward a year, and I was getting some service done at JC. They noticed that the insulation on a negative wire coming from the 12-volt panel was burnt. They traced the length of the burnt wire from the distribution panel for about 5 or 6 feet - from then on it was OK. When they removed the plastic inside end cap on the front of the AS, there was a slash-like burn mark in the plastic. JC also found that one of the breakers needed replacing, and did so.
Having previously had a 12-volt fuse-type distribution panel in a 1994 AS LY motor-home, I much prefer the breaker-type in my '87 Excella.
1987 Excella 32-foot
1999 Dodge Ram 2500HD Diesel