Constant outside air temperature displayed in dash

[brasiliangringo]

The ambient temperature display measures a fixed 78-79Farenheit & never changes. I have used VAG Com and there are no error codes reported on the outside temp sensor which is positioned behind the front bumper. I also unplugged it at the 'plug end'(fairly sure it was the right plug - passenger side under and next to small filler tank - hydraulics) and the dash ambient temp reading remained the same ie 78F - even with the sensor disconnected ?! Yes, it is a UK car, so not sure why its not in C.

Should also add the dash has a faulty water temp gauge which is a cluster issue..

Any ideas?
2000 c5 A6 Avant 2.4

[elan2s]

Assume the air con displays are also in F. To switch to C

Press and hold the recirculation button. Then press the temperature up ("+") button to switch between degrees Celsius & Fahrenheit on the Climate Control Temperature and Instrument Panel Outside Temperature displays.

As to why the temp is stuck can't help you on that, may be related to the cluster issue