An unexpected spark
I was wiring a temporary plug onto the end of the hot water heater circuit in my 76 argosy today.
Touched the metal plug housing to the positive battery terminal and surprise! Sparks! The AC circuit was OFF.
It took a minute to figure it out.
The metal housing on the AC plug is bonded to the AC ground which is bonded directly to the trailer frame as is the battery negative. = closed circuit
probably a really unlikely event but worth noting anyways, because at certain times while working on things there are a lot of DC hots floating around, and any tool or appliance with a grounded metal housing would create this effect.
Solution don't be an idiot like me with Dc hots floating around