Hello all, new here, thanks for listening. I have a 2-3 year old Sta-Rite Max-E Therm 220HD heater for my spa at my rv park. It will fire up properly and heat the desired temp (102), but then it won't restart as needed when temp drops. If I turn the unit off/on, it will again start up and heat, but will not restart automatically when more heat is needed. When this fault happens, the red "Service Heater" light comes on and no codes under the cover. This fault happens only after the unit has tried to start three times. Again, thanks in advance. Bryan