So my dryer gas valve does not stay on, and sometimes never lights. So Ive traced out the the igniter,highlimit and t state, flam detector circuit. All seems to be functioning. I changed both t states, thinking maybe a set point problem. What happens is I start dryer, I see igniter glow, I think that then the flame detector opens and gas valve fires, with in a few seconds valve closes? I took the flame detector out and replaced it with a temporary switch. Again with switch closed, igniter glows and when I toggle switch open gas comes on, and shuts off. Two questions, flame detector is normally closed and opens on flame and stays open correct? second question I think mother board is bad, I checked moisture sensor and it is open normal? Any thoughts? Then I think that flame detector circuit is all supposed to be normally closed condition to fire gas valve, but when I toggle it open with a switch that is when the valve opens. Bad board? Someone know how the logic is? Thanks

you know I just thought that maybe the flame is to high and it is tripping the low limit t stat as soon as it fires, I will test that theory tomorrow, can someone explain if there is away to adjust the flame down? Thanks

So I read some more and it seems that the sequence is that you push start, valve 1 opens, igniter comes on, flame detector opens, valve 2 opens, igniter goes off, flame on drying. So that seems to work, leading me back to the board or to much flame, and valve adjustment says to be full open?

OK all is working fine after checking all wiring, testing component's, and finally understanding how the logic sequence works. It was the high limit that would not reset. I replaced it, and while testing everything I neglected to understand that air flow is key to function. Gas valve would not stay on while I had the machine apart due to no air flow path. I cleaned every bit of lint out of the entire system which I believe is the major cause for most failure's in a dryer. So the moral to the story is clean your stuff regularly. Good Luck