Reverse Polarity all of a sudden

[grewvin1]

Same power outlet, same cable, three month ago marina added GFI 15amp. All was fine but if refrig, and battery charger kicked in same time blew GFI. Added Split harness two plugs to get 30amp to panel. Oh yea it is a 32ft 1985 Wellcraft St Tropez. Switched the double panel switch and now get "reverse polarity" light on and panel will not operate properly. Why would it go to rev. polarity?

 

[dingbat]

The negative and positive leads where swapped somewhere. Either in the outlets or your harness.

An AC circuit tester will determine which one.