Here's one solution, a cheaper bodge from our 911 friends.
911uk.com - Porsche Forum : View topic - Internal cabin temperature sensor failure / replacement
Older Porsche owners have tracked down their Thermistor Specs for 924s etc. They found the Thermistor specs in data sheets a residence at say 25 degrees and then the rate that resistance varies with temperature.
If anyone has access to this information for the 986 then thermistors are about 75p a lot cheaper that £300 for the replacement part or even £80 for a second hand one!
Does anyone know where we can get the data?