Trial found that burns bright red light, as thermocouple sensor to the flame, analysis the reason may be a fire is too small. Adjusting fire knob (potentiometer) shall be null and void. Fire control potentiometer resistance changes to normal. Try the "ability" potentiometer on the control panel, clockwise (" ability "), about 30. After the commissioning, the fire has been enhanced, not stall, and burns red light, everything is ok.Y5aservice manual download site