Those battery disconnects are more trouble than they are worth. They really give you a false sense of security. They either wouldn't engage and make connection and come on, or would connect and the internal connection wouldn't be solid and I would have dim lights etc. But of course the worse part is if you need to use your rig and you push the rocker switches and nothing happens. This is seriously aggravating. So I took some heavy cable and just wired around them so that the system is always on. If I need to disconnect the coach and chassis when in storage mode, I just disconnect the negative battery cables, which also gives me a chance to inspect the battery for water and corrosion at the cables.
The disconnects on an rv are a bad idea I think, because like some else said, they corrode on the inside and you can't tell if they are working properly and conducting power at the correct amperage. So even if they seem to be working properly they may have internal resistance because of corrosion. I have taken them apart and believe me they do corrode. This means that when they are in the on mode and connecting the batteries to either the coach or chassis the batteries may not be getting the full charge they need and also not providing the full power that is needed for the coach and the chassis, which could result in failures of some circuits and possibly even fry a motor or circuit board. I know that sounds a little extreme but battery disconnects are definitely a weak link in your electrical system. I'd rather live without them than worry about them!!!
