Not staying lit - Goodman GMS80453ANA Open Flame Mid-Size Heater

Remove the front panel and tape down the door safety switch so the unit can turn on when door is off. Turn up thermostat to make sure there is a call for heat. The circuit board should indicate a call for heat with either a blinking light or a solid light. Then the exhaust fan should turn on clearing the venting from any fumes. When the fan has ran for a few seconds, the igniter should start glowing orange. After it reaches a predetermined temperature, the gas valve should open with a click. The flame will start at the burner closest to the igniter and travel away from the igniter. There is a small flame rod located in the flame path on the last burner that tells the circuit board it feels the flame. If the flame goes off within a few seconds of starting, you have a dirty flame rod. Clean it with a scotch-brite pad. Once you get the flame to stay on for 90 seconds or so, the room air blower will turn on. If it tries 2 or 3 times to start but does not, the circuit board will record a code and display it with a blinking light. Look on the door panel for a wiring diagram. There will also be a Diagnostic chart that will tell you what the pattern of blinking lights represent.

Good Luck!