I've got about a 12ga wire that looks almost like a female coax plug, any ideas? It's in a plug with two other wires and plugs into a relay on the left side of the engine side of the firewall. I've never seen one like it so maybe it's a remover?

 

Sounds like it's the high speed feed wire for the AC/htr blower motor. That "female coax" houses a 30 amp fuse.....