I have a dual stage furnace. most of the time it works fine but 1 or 2 times a day it calls for heat, inducer motor starts, it lights up and the blower starts, after the blower being on 10 seconds the inducer slows down and the burners cut out. The blower goes for a bit and then turn off and the inducer starts again to start the process. But now the pressure switch on the condensate line clicks and when it comes time to start the burner it will not even start. The next time it starts hard and it still goes out. It does this for 10 -15 minutes each time getting better until it finally goes back to normal. I am trying to find out what the issue could be as we have checked the pressure switches themselves, the flame indicator and gas line. Frigidaire

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    I'm no expert on this, but it sounds like a flame sensor. I have a boiler (US Boiler, K2) for hydronic heat in my home and it did almost the same thing: Combustion blower would start, then the gas valve would open, burn for a few seconds and then go out. It tried 3 times and then went into a soft fault and wouldn't retry for 15 minutes. I found instructions online for yearly maintenance which is basically cleaning out the condensate trap, removing the flame sensor and gently scrape off any debris with a Scotch brite pad. It works about 90% better now. Your mileage may vary! No promises. – George Anderson Mar 1 at 22:01

If this is a condensing furnace, make sure that all the condensate drains are open and not plugged with dirt. There is also a "drain trap" that may need to be flushed with water to clean it out. When the furnace fails count the flashes of the red light on the circuit board and it may indicate where the failure is.


Check the drain pipes and also you need to check the fail-safe switches.

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    While this may well help the OP, we do like answers with some explanation to them. I'm sure you've noticed that in your brief experience here across the SE sites you've visited. Please feel free to edit your answer to include a little more to help the OP out. – FreeMan Mar 2 at 14:47

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