pep boys sells a trailer wiring kit that does not put a load ont he car's electrical system as it is wired with its own power formt he battery.
I just bought one for my dad's 97 Range ROver 4.6 hse. so we can wire upt he trailer to it, even though we have my brothers 1993 range rover 4.2 to tow it.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.