Tick noise in the rear area

Hello, I’m new, since August 1%-leasing driver,3D, 240hp BJ 02/09, 75000Km and I’m not a mechanic myself, don’t understand much of the car either. I’m completely satisfied but now where it’s cold, I have a ticking noise at the back left. This ticking noise is about like an old mechanical alarm clock that ticks too loud. always at the same intervals. Was at friendly, which probably didn’t often have to do with the Phaeton but he is the only VW dealer in the place. First he said, it’s probably the magnetic switch for diesel supply and after the examination he said, it’s the heat supply for the diesel engine, which is activated only in the minus degree so that the engine has enough heat, since the diesel engine does not produce enough heat accordingly in the winter. This noise is so loud that you can even hear in the vehicle at closed doors, of course only in the stand. Does anyone have similar experience? Can this be normal? Have Audi A6, even diesel driven and I don’t know that.