Furnace problem!

[311Hemi]

Furnace has been working off and on at the end of last year and the few days this fall.

I will hear it ignite and burn for a few seconds then go out. They it will attempt to reignite, burn for a few seconds and then go out again.

I am thinking the thermocouple needs to be replaced....but any other thoughts?

[Borch]

The rapid cycling is a symptom of the sensor probe either malfunctioning due to crud build up or a faulty part.

Mine has needed to be pulled a few times over the years to clean off the white crud that for some reason accumilates there. Use a little steel wool to clean it off and reinstall and it works fine.

[IFallsRon]

I had a similiar problem with a Lennox model. It would work fine after cleaning or replacing the sensor. The furnace guy eventually replaced the probe with an electronic system.

[Heidi]

I just spent $353 to replace a circut board that had a burned out piece on it. I kept restarting the furnace, per

the instructions, but it kept going out so I had to call in

a guy. The repair guy said it was just one of those things.

[fishfart]

Ditto what borch said, mine had crud on the flame sensor.

[eurolarva]

We had a cracked heat exchanger and it had the same symptoms mentioned. If we left the door off it would work fine. Super dangerous if this is the case. The only way we knew what was happening was our carbon monoxide detector went off and we called Minnegasco.

[311Hemi]

After digging in to it I don't have a thermocouple, it has the flame sensor. I cleaned it off and it still did not work. Somehow the negative pressure switch was stuck in the open position so the blower would not start at all (there was a blinking light code saying it was a pressure switch). I pulled the hose and cleaned it, put it all back together and it fired up right away. Not sure these are the correct terms as I am not an HVAC guy!!

Thanks for the info!!!

[BoxMN]

Same thing happenend to me in my intake vent. I must have been blowing leaves when it was on, as it sucked up some leaf debris. I just had to pop the pvc pipe off where it enters the furnace, clean the leaf debris out, and it has been flawless since. First thing to try now The blinking lights told the furnace guy on the phone what was going on, and he told me what to try. Sometimes technology is good saved him from needing to come out!

[311Hemi]

I will have to check the vent outside. I actually pulled the hose of the valve in the furnace and cleaned the dust out of it. I didn't even check the outside vent. Good to know.

[UMDSportsman]

I think my father had somewhat of a similar problem, it would start, then shut off, but i can't remember all the symptoms. what it ended up being was on the drain, there was a baffle and it was plugged, causing a backup of water, which shut it off, we took it apart, cleaned it and it worked just fine. I do not know what they have for a furnace, or what the exact symptoms were, just something i remember helping with. might be related, might not.