Thanks Reno, I had toyed with that idea in my head. I’ll give it a shot tomorrow. Nothing to lose I suppose.Maybe this will help, maybe not. We just had the same heater, but 250K, that wouldn't fire up. Replaced literally everything on it before we finally figure out the gas valve was bad (this happens when you have a new tech). But, after we swapped out the valve, the "old" inlet pressure of 10 wasn't enough to light with the new valve. We bumped the pressure up to 13 (the proper range is 10-13) and it has been working fine ever since. I guess the point is, sometimes you can have an issue small enough that won't allow the heater to work properly, even "within range". Try changing inlet pressure to the higher side of the range. I'M NOT SUGGESTING YOU GO OUTSIDE OF THAT RANGE!