Hi Guys...I would like to reopen this thread.
I have a Freedom 90 two stage variable speed furnace that was installed when my house was built in '99 - and I've had this EXACT same problem since it was installed. My furnace fails EVERY year, sometimes more than once. The problem usually ends up being crap in the burners, crap in the orifices or a dirty flame sensor. The symptoms are always the same - the flame does not propagate across all 6 burners fast enough to get sensed before the furnace shuts off the gas. The 'funny' part is that it usually lights - just not fast enough to heat up the sensor quickly enough to get sensed before shutting down (the last burner barely gets lit and it all shuts off). If the furnace waited just a half second longer to sense the flame, it would be reliable. Apparently, this 'wait' time is not adjustable.
In addition to my twice annual cleanings, I usually end up paying for one or two emergency repairs throughout the heating season. I've had the burners, the gas valve and various other electronics replaced. I'm on propane, with a 500 gallon buried tank, with regulators on both the tank and just outside the house. I have never serviced the furnace myself - it's always been done by the company that installed it. Every time they send a new rep, he goes through the same checkes, comes up with new theories, and none of them ever pan out. They have resorted to telling me that it's moisture in the propane causing rust and crap buildup, and there's nothing they can do about it. They have gone so far as to tell me that even if I replace the furnace, I'll likely have the same problem.
So the bottom line is that I've been to a pro, with no success. I'm convinced that this furnace has a major design flaw, and as an engineer, I really want to talk to someone at American Standard. Unfortunately, they don't talk to us peasants. They only talk to pros. I keep wondering if there has been an EC that may have already been released that can be applied to my furnace, but since I can't ask them (and my installer keeps telling me that they've talked to AS), I'm at a dead end.
Does anyone have any thoughts or recommendations? Does anybody know anyone at American Standard that I can call? I'm about ready to call in the DIY network or HGTV and see if they want to do a segment on my furnace...because I'm broke from paying for repairs.