It's not that cold...

[The_Laird]

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?