My neighbour across the road picked up his new caravan last weekend but when he connected up the electrics the brake lights on the caravan did not work and he was off for the weekend like you do to try out the caravan, we have a local tow bar fitter who fitted the tow bar and the electrics, a quick phone call and off he went back to the fitter who checked out the electrics and all was working ok, but what was required was a relay to be connected to the wiring loom which solved the problem, is this a common problem because of the electrics which are now on caravans,