If you mean the snoke was billowing from that exhaust? then that the aux heater, it's not there to provide heat for the rear internal heater? it's there to provide heat for the engine to aid warm up times and to provide heat for both heater units
due to the TDI engine being so efficient and crap at provideing heat they fitted the aux heater, it burns fuel taken from the fuul tank via a seperate pump and metering unit, the most common cause of excessive smoke is a duff glow plug, the replacement of this is covered on another forum that I used to frequent
I cant post you the link to the topic as I'm banned from the site
not