Unit operating with cover removed, unit kept defaulting to trap filling mode and when coming out of it it would turn system off like there was no call for heat and supply temperature would quickly increase with pumps on and no flame ramping up then default back to trap filling. Could be a glitch in the control due to being cold or it could be sporadically failing. Determine EA code to possibly be from ignitor leaking and recirculation in boiler cabinet. Combustion motor sounds like it's on its way out as well. Changed ignitor system was running fine without cover and with it on now. Recommend PSA