Sta Rite heater, with a 42001-0096 Board, this replaced my HD board which was an HD board (don't see the PN on the board).
Last year or so the heater would not turn on and stated service heater. (the display was pretty much gone, so can't say what the error code was), but I figured it was the Flue switch, because if I disconnected and connected the wires together my heater would work. Problem is that the water temp coming out could sometimes get to almost scolding. So since the Flue switch was broken and my HD board seemed questionable I bought the above mentioned 42001-0096 and I bought a Flue sensor. Installing the flue sensor, netted the same thing, service heater (no errors). But it would not allow the heater to ignite. Again connecting the wires from the board directly together bypassing the sensor allowed the heater to ignite, but again you would have to be careful because the water would be darn hot after a while.
I've bought 2 flue sensors now because I didn't trust the resistance on the first one, 70 degree temp it was reading 6.5, while the new one read 4.5, figured the first one was bad, but trying to figure out what the resistance should be based on a normal temp seems to escape me.
So since this is not an HD board, the standard flue sensor (screws in and has 2 wires coming out, vs the switch that was revetted in and worked with my old HD board) should work.
I'm really trying to figure out what is going on, the parts seem right, this should work and it's not. Can someone tell me how I'm failing to fix this? Where at least 2 of my flaws lie?

Thanks
Tory