We determined recently that our 2011 VW Golf Variant TDI wagon has an electric auxiliary heater element; the wiring diagrams label it as an "option" (7E6) that's not indicated on the vehicle information sticker. I don't have wiring diagrams for B8 A5 TDIs, but I'll wager that your car should have a couple of 40-60 A fuses in Fuse Panel B (engine compartment) and a fuse position in Panel C for the auxiliary heater control module. Even that little bit of heat helps when the polar vortex hits & the diesel isn't up to temperature yet. --g