Was replacing the alternator in my 2013 5.0l and just as I was about to remove it realized one of the wires from the plug was not connected which has likely been causing all of my issues. Completely new to wiring so asking for general advice on what I should do here, I bought another alternator from a parts truck with 3 wires that I guess I could strip and connect to the wiring, just unsure if it would be easier to just do something with the plug that’s currently in there. I have attached photos of the plug from the new alternator (3 exposed wires) and the plug that’s currently in there (one red wire loose).

 

Welcome to the forum.

 

If it were me, I’d use the connector you got with the replacement used alternator, and splice, solder, heat shrink to the three wires going to your existing connector. Plug that into your existing alternator and see if that fixes your issues.

this connector/harness repair will have to be done either way, so no time/effort lost.

all this assumes that the connectors are the same.