After the engin upgrade to a 200tdi, the roof lights no longer work. The were wired up to the full beam and I believe they were powered off of the altinator. The air horn was on a relay and definately wired up to the alt and the guy who fitted the engine didn't reconnect. I've taken the air horn out and wired up the normal horn but I can't find the wire for the lights. Any idea where the cable could be. I can only see one wire coming from the lighting bar so I'm guessing it's a negative earth. If I can find the cable bearing in mind it's wired to the full beam, where would be a good place to pick up a live.