Trace has been discontinued for almost 20 years. They were a product of a Merger between Trace and Heart to form Xantrex. It is AMAZING that your Trace still functions. Trace had a lot of reliability problems with their RV Inverter/Chargers 20 years ago. I would contac Xantrex and give them your Trace Model number and see if they have a current replacement that will work with your Trace. What the Battery sensor does, is monitor the temp of the battery bank and drops the charge rate if the battery bank starts to get to hot. I would just unplug the Temp sensor until you figure out what to do. Most Inverter/Chargers, while they usually supply the temp sensor in the box, a lot of times, they were not really used. Doug