1999 Vangaurd Cutaway Class C electrical issues

Question

I am posting for a friend of mine who just bought a used Vangaurd Class C. The Motorhome is in overall great condition, but there is one issue we found. When running off the house batteries we noticed the fridge, furnace, and tank level monitor will not turn on. Everything works fine when running off A/C power. There is a switch inside that has 3 positions (generator/house/converter). What we observed is that when switched to converter (motorhome plugged into AC) that all the DC fused lines are at 12V as they should be, but when we switch to the house batteries all the DC fused lines measure -12V. These measurments are taken inside the fuse/breaker panel. We also measured the same thing at the back of the fridge. The fridge will work off propane and 12VDC as long as the motorhome is powered through the conveter and the the motorhome is getting AC power.

Does anyone know why this is? Is there something wired backwards, or is a -12VDC ok? The lights, waterpump, and water heater still turn on when switched to house battery, just the fridge, furnace, and tank monitor that don't turn on.

Thank you,

2oldman · Answer

Boy that is a puzzle.  It *almost* sounds like the batteries are in reverse polarity.  But if that were the case, the things you describe as running would not.. or run backwards.

mr_p1 · Answer

Yeah, I know my leads were not reveresed, I would hold them there and watch the voltage go from positive to negative just by switching from the converter to house batteries. The problem is, I do not know what wires are reversed, at the switch? I don't want to short something out and cause more damage. I can't even pull the switch out from the wall, there is zero slack in the wiring.

Thanks for the responce :)

paulj2 · Answer

I would say batteries are connected backwards, easy to do. Less likely the switch wires would ever be messed with. Lights don't care about polarity, some appliences care and others not.

mr_p1 · Answer

I would have thought you would be shorting the batteries if they are connected backwards, as it looked like the are connected to the chassis frame.  The battery compartment is small so was hard to see, so I will double check it, perhaps pull the batteries right out.  Thank you.

mandalay_parr · Answer

PaulJ2 wrote:I would say batteries are connected backwards, easy to do. Less likely the switch wires would ever be messed with. Lights don't care about polarity, some appliences care and others not.X2

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1999 Vangaurd Cutaway Class C electrical issues

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