+1 on late-80's vintage power converters. Mine is the original, but I'm kinda hoping for the day when I can replace it with a newer design. My 2 12v batts stay charged up ok SFAICT, but a modern converter makes all the diff. in the world. Remember also that your current one does NOT charge the engine battery when the unit is sitting - only the alternator does. I bought a Trik-L charge unit that steals a little bit of juice from the two coach batteries to keep the engine batt charged up when on shore power or genny.
The genny needs a tune up. Remember also that the fuel pickup will not draw when the main tank gets down to around 1/4 full or so. Run the genny for a half hour, with load (AC & Fridge) every month. Gennys NEED to be run. They also use oil as part of their operation so make sure you check it each month.
There are a bunch of 87/88/89 vintage Bounder owners here, so feel free to ask away. I have most of the original docs that came with mine too, so if you're on the Chev chassis with the 454, I can help with reference questions.
