It will flame-out before the thermostat is satisfied. I suspect it is the little thing in the center of the photo. It's round, black, with 2 push-on wires and a red button? in the middle. I suspect it because when i first opened the furnace up, it was only held down with one screw and it was sitting up at an angle. when i screwed it down tight, it worked for a while. there are 2 of those things. one on each side of the burner box. the one in the photo is on the top. the other is on the bottom. What is it? can i get a replacement? will it fit it? Thanks