Customer reported pool heater turning on and off. Upon arrival turned system on. System started. Pool began heating. Expansion valve was operating. Pool temperature went from 68 degrees to 100 degrees. Pool heater tripped once at that temperature. Continued to trip. Possible non-condensable or debris floating in system. Customer approved that systems refrigerant be removed, evacuated and recharged with refrigerant. Completed suggested repair. Pool heater achieved 103 degrees and also restarted when temperature was increased further. Working to manufactures specifications.