Hi folks ... Not posted for a bit as everything going ok with nearly 18 months of touring . But !!! just had an issue with IDC , BPW's version of ATC ... Its worked fine and then all of a sudden, no self test and Green led ..... Service engineer was coming for annual service asked him to have a look , He said never seen this fault quoted approx. £900 for new unit but it might be wiring fault and to leave it with him ,three days later ,I thought I'd check where all the wiring went . Really quite simple underneath the sensor wires disappearing to middle of van. Led wires and White and Orange main feed and earth into unit . Main feed plug had traces of Verdigris from it so whipped it out lo and behold electrically dirty ,all cleaned up trailer plug refitted in Tiguan (13pin ) and Whir whir self test and led green and steady . Fixed in 10 mins . Question any one know exactly where white and the orange cables go in the transformer box (couldn't see with out stripping it out but found the wires ) And any one power the plug up from the socket I assume its pin 9 and 3 to give permanent live from car to the unit