Hi,
The sensor is a part that we'd need to replace for you. If the unit is out of warranty, then the cost to replace it is $34 plus shipping. If you're certain that is the problem then please send it in to:
Tunze USA
305 Victor Street
Austin, TX 78753
Please include your return address and a telephone number. We'll get in touch within a day or two of receiving it to arrange payment.
If you have any other questions, please just let us know.