I ordered some of these http://parts.digikey.com/1/parts/953501-thermistor-ntc-100k-ohm-5-do-35-104jg1jra.html to test with. They are 100k which is a good resistance level for the circuit. Thats at 25c. I will do some normal ambient measurement inside the system and if they're say 35c normally, then I'll an appropriate resistor in series with the thermistor. It's a test and a work in progress, but it was only 90cents a piece, so I'll see.