Returned with sensor but the sensor I brought would not work to replace the current sensor. Went ahead and ran a combustion test while I was here and found water heater burning off over 1200 ppm of CO. Pool burner assembly and found large amount of buildup and dirt in the burners. This is what’s causing the sensor to trip. Cleaned out burner Assembly and reinstalled. Unit is now burning 22 ppm. All OK at this time.