Developments ,we installed a new fuel filter this arvo bled the ,filled the filter housing with fresh diesel ,and it started up ,a bit fluttery at first but settled down ok after a while ,then we moved on t0 the wireing we determined that the big green wire was in fact earthed to the body ,we installed that in the 7 pin ,then put it in reverse and set of the reversing buzzer ,proceeded to connect spare wires to the one wire we knew went to the lid switch on the old socket ,buzzer kept buzzing ,then connected test light [led] to the body earth ,and found all the wires required l and r indicator, brake /tail ,and reverse ,we havent had it connected to a trailer yet but ,tests ok ,my son was assured he would need the socket with a lid switch ,so thats what threw us ,we will just have to get used to it beeping in reverse when the trailer is connected ,pugs