Today was going to be the last swim so I set the heater to 89 and jumped in. We jumped in and had some fun. I checked the error messages when I got out and it read- sensor failure. As per the manual- Thermistor temperatures disagree by more than 2F. Also Water Sw Open. This may be because I was running the pump at a slow speed. I know these are new errors as I cleared the memory 2 weeks ago, and I have been checking. The sensor error was listed as the last error. I don't know about the sensor failure, what that means, how to trouble shoot, how to repair. Thanks. (The heater is listed in my signature, this is the new one I installed about 1 month ago.)