Re: 147 Outside Temperature Sensor
Presumably you are still having the same problem when you are driving along (with air flowing past it) yes? Obviously, if the car has been standing in the sun, the mirror will have warmed up and it will give an incorrect reading until you've gone a couple of miles.
If the sensor is totally buggered, it tends to read -18C (I guess that's open-circuit).
The sensor is removable and can be replaced with the aid of a soldering iron on the wires inside the mirror cowling. But I don't think you can buy just the sensor on its own (unless someone were selling one on ebay) so you'll have to buy a whole mirror unit I'm afraid. Again though, look on ebay or check out breakers, the mirror will likely cost you about £120 from a dealer otherwise!