I have an Aquastar 38B tankless hot water heater that will not produce hot water. The pilot lights just fine and stays lit. I set it to the on position and the burners light up even though no water is flowing but that's not really the problem. When I turn on the hot water the burners should light up and heat the coils to make hot water but instead the burners turn off and do nothing. No hot water. When I turn the hot water off the burners light up again even though there is no water flowing. I'm stumped. I have cleaned the filter and tested the water pressure and gas pressure through the regulator. Everything seems to be working correctly but no flame and no hot water although the pilot stays lit. Please help.