Just thinking here ,do you need to change the coding for Aux heater to show in the mmi screen , do a full scan with vcds and see if aux heater pulls up in the scan results .
On the 4.2 tdi the exhaust of the aux heater sticks out through the under tray just in front of the drivers side front wheel , is it the same for 3L tdi I'm not sure ??
Search on interweb for thread on a8 called definitive guide to auxillary heater or summat like that , it tells you everything about how to do it
I'm not sure if all 3L have it some one on here may know .
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