Hooking up RV Battery - which wires are positive/negative? - Yahoo! Answers
RV.Net Open Roads Forum: Do It Yourself Modifications and Upgrades (DIY): Battery wiring
Wandering Free.com » Basic 12 volt Electricial color codes for wiring Rv accessories
Weather permitting, I will take a look at my RV tomorrow.
Here is what I posted in my note above: "In a house, black is AC hot, red is AC hot in a two phase 220 v AC circuit. White is neutral. Green is ground. But this has absolutely nothing to do with DC battery connections in a car or trailer."
It does apply to the 115 VAC supply in a RV. It has to be darn confusing to have black as AC hot, but black as DC negative when both AC and DC are present in a RV. In one of the links above, they refer to inside the RV color code vs outside to the battery color code.
In house electrical wiring, neutral (white) and ground (I stated green, which is true when it is insulated - but bare wire is what is in romex) are physically and electrically tied together at the main breaker box.
Regardless of what the color, by code, should be, the only way to be certain is to either physically trace the wires, or use a DVM and check either resistance or voltage with the battery disconnected as outlined in the posts above.
Since he switched the connections, he had to have had it backwards once. I hope he will have the system checked by a qualified professional.
I have worked for decades on electronics design and repair where white is positive and black is ground. I have to keep reminding myself that back is AC hot when doing simple maintenance around the house. It drives me nuts.