Given that I happen to know it's a balmy 5c outside and the OAT display in my GSi says it's anywhere between 16c and 28c as I'm driving along, I'm getting an idea that the sensor has quite possibly finally had enough.
Understandable as it's quite likely the original part and has been getting everything the weather and roads have thrown at it since Oct 2004.
So just out of interest and curiousity....
I'm assuming it's a bi-metallic type working by variation of resistance due to temperature. So does anyone happen to know the resistance range of a known good sensor at normal indoor room temperature ?