katysdad wrote:
hopefully OP has solved problem. If not I have seen wires get loose or pulled out of replacement 7 way plug on trailer pigtail and short or power a circuit inadvertently. Wintertime towing can fill them with road chemicals and corrode all the connections in them also. Always recommend replacing with new cord and molded plug.
A molded cord is a good idea. I have had good luck by after checking to make sure all is good, then putting enough silicone sealer to fill the cap. Water can't get in, and nothing can shake loose.