I'm reopening this topic because I have the same issue. Last camping trip last Fall I discovered I had no DC power, though it was fine previously. As things go, I put off 'running it to ground', so to speak, until things warmed up this spring. Now I'm 10 days away from an important trip (!).
I have a WFCO 8725 converter, and have rewired the rat's nest with terminal strips, so everything is easy to check. All fuses are good, including at the battery. I've been trying to maintain the battery by charging a day or two each month, but you know how that goes; a day becomes a week, then a month... When I first checked, the battery was providing an even 13.5vdc, and I found 13.5v on all four circuits -- but when I added a load, power went to zero. A day later, I'm now getting 20vdc? (!) at the battery , and 10v at the circuits. Still, nothing works, even the LED lights. Should I assume the (relatively recent) battery is toast? The converter seems fine -- at least everything works on shore power.
Alex Sproul
'05 Classic
'02 Suburban
Alex Sproul