Hello,Not had an Audi for many years just bought A4 2000 TDi thought i would try,done a few things as you would expect cars age but seems fine heater not best and temp i think a little low ,Can anyone confirm is this a common problem or is there a way of sorting out,,hope to hear from you soon ,best regards Coxie 

Hi Dave...welcome to the Forum

Common fault with coolant temperature sensors & connector/wiring to it but if it's not blowing hot I would recommend back flushing the cooling system to ensure it is clear. Also worth checking the diverter valve to see that hot coolant can flow....check with temperature gun is easiest.

Let us know how you get on with it

Cheers   Trevor