Steve, you would have to unsolder and resolder four wires that are about the diameter of a pin. It is not an easy task and if you overheat something it is ruined. Sensor failures are not very common, the sensors are not listed as a spare part or offered as one. To get sensors I have to make a request and it has to be approved by Mr Michelle, the head electrician at Tunze.
marrstarr- I have sensors in transit right now from the factory, I will have them toward the end of next week if you want to send it in. I don't need anything except the actual controller.
Tunze USA
1304 Monica St
Austin TX 78758