It's not that cold...

[IceBlue8]

Had a few problems with the exterior temperature display. Initially, it was reading around 4C too cool, so those nice guys at A8 Parts sent me a replacement sensor. Fitting that was fun - you need fingers that are 8inches long and no wider than a ****tail stick!
Anyway, that didn't fix it and it was reading around 6-9C too cold.
So I fitted another replacement sensor yesterday (FOC from the aforementioned nice guys)and when I started out this morning it was reading -34.5C! Now, I know I live in Scotland but it's not that cold. Anyway, on the way it started to rise rapidly and settled down at a plausible 5.5C.
The question is, what's going on. Do I need to calibrate the sensor somehow?

[IceBlue8]

It seems to reset to -40C every time I turn off the ignition and then rise slowly for a few miles. It then rises quite rapidly and settles down at what seems to be a 'real' reading - currently about 5C or less. This is unique to the latest sensor - the previous ones just read a few degrees low.
Any ideas- or have I baffled the experts?

[IceBlue8]

The guys at A for Audi tried a brand new sensor - still no luck. I've tried 3 sensors now and checked that the connection below the n/s headlight is good. But it still reads -40C every time I turn on the ignition and takes around 10 minutes to get to the 'real' temperature. And then it seems to work OK until I turn off the ignition again, when it goes back to -40C and again takes 10 minutes to read correctly.

Are there any auto-electricians out there who have any ideas?

[PsYcHe]

Could be a problem with the unit that the sensor plugs into then.