Hi, just inherited an A6 3.0 tdi Avant as a company car, and the previous driver never told anyone that it comes up to temp on the dash gauge but the heater never gets hot, luke warm at best.

The car is highly specced, full heated leather etc but having the heated seat on all the time is getting boring now.

Does anyone have any ideas as to the problem.

Maybe worth flushing the heater system through....messy but effective!

May seem basic but check the fuse first, it's quick easy, I'm not sure if there's is one for anything particular on the A6 but worth a quick look-see. 

Hi had the same issue on my car 1st is the fan blowing try putting heater on full fan and feel to see if it blows at the vents if not its the fan itself part number 4F0820020A if they do blow check the coolant level is upto max mark as heater matrix is the highest part of cooling system if this is ok then you then may need to check the Heater Control Valve 4F2959617B see this video on youtube 

hope this helps

Mel.