Secondary furnace is driving me nuts. The unit is an ICP LP Furnace Model #t9mpd050f12a3. I noticed about a month ago that when the unit was on, the blue flame would pulse every second from normal to somewhat weaker flame but not close to going out, just slightly weaker. I didn't think too much about it but the furnace has since stopped working. It's displaying 6 led pulses. I have another unit that is not having any issues and I've been able to pull parts to test with and so far have tested: [b]Gas valve[/b] (got a new one) [b]Pressure switch[/b] - swapped with the one working from the other furnace with no change. Tested the original with a multimeter and it's working properly. [b]Igniter and flame sensor[/b] - swapped with other unit with no change in result [b]Removed filter Cleaned small wasp nest from air intake line[/b] Runs through the standard startup process but it seems like the gas valve never opens. Fortunately, this is the 2nd floor unit and heat rises from the first floor but on the really cold nights, it's needed to keep the air temp consisent (and if we want to close the doors to the bedrooms) Not sure what else to test other than a new circuit board. Any thoughts or suggestions? thanks, Jim

I have a goodman gmpn080-4 that is about 20 years old and stilll works fine. I have had little trouble with it in those 20 years. I was thinking it is time to replace it. I want something with a 92 to 96 percent efficiency. single stage heating and cooling. I know that some of you work on lots of furnaces and if you were going to replace this one which brand would you use for the least amount of problems and the greatest reliability? I have been talking to people with the goodman two stage and have heard about lots of problems and service calls. what is your suggestion?