The unit displays no flow. The Error codes are 175 and 182. However when I power off the unit and then turn it back on, the system works; flow is detected, the cell reverses etc. It's only in the morning when it's been running all night that it reflects the error codes and no flow. Also when the chlorinator is working the circuit board gets fairly warm. Is this normal? The sensor is about five years old. Any advice would be greatly appreciated. Thank you