New batteries, good opportunity for a reversed polarity which pops the converter fuses for that. (maybe two 30a fuses on the DC fuse panel or else on the converter)
So you are on battery with the wires reversed, the lights work, but the fans run backwards.
If red and white, red is pos. If red and black, red is pos. If black and white , black is pos.
The battery monitor is a rough voltmeter. A full battery is 12.7v, so the converter at 13.6 will show as full even if the battery is nearly dead. With no converter (as now) it will show the actual battery state (roughly)
