Furnace flame sensor?

Messages
9,117
Location
Illinois
Just noticed with the furnace... it has been running for at least 15 minutes, putting out heat. I walk out into the garage and it doesn't sound right. I looked at it, and it was in the middle of relighting the burners, when it should have been running continuously for another 15 minutes or so. OK... so that's a problem. I put a new main control board on it in January of 2014, after the previous baord started failing (blinking LED light indicated "replace board"). The furnace is nearly 20 years old, a Trane 92% efficient unit. Flame sensor dirty / flaking out? Thermostat flaking out? (Dropped a call for heat, and then started calling for heat again?) Control board flaking out (again)? If it was a flaky/failing flame sensor, would have it re-fired without shutting completely down first? No code was being flashed by the LED on the control board. mad
 
Messages
1,125
Location
USA
My flame sensor seems to need cleaning once a year, at least. When it's bad, mine ignites, runs for about 15 seconds then shuts the gas off. I don't remember how long before it starts the whole cycle over again, but it definitely shuts down completely between attempts. It's a Ruud from about 2000. If it's easy to access, I'd at least give a shot at cleaning it. I just rub it with a Scotchbrite pad
 
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Messages
1,841
Location
.
Sounds like the igniter could be going out, but it is completing the circuit enough not to throw a code. Usually its code 12 though.
 
Messages
452
Location
Midwest
Clean in off with some sand paper. Well, that worked for me on my newer gas furnace. I do it once a year now.
 
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mrsilv04

Thread starter
Messages
9,117
Location
Illinois
I had a new flame sensor in the cabinet, I bought it when I bought the new control board in January. I put it on this morning... why not. I also bought a new ignitor back then as well.... I probably should just go ahead and put it on too.
 
Messages
6,095
Location
Baltimore, Maryland, USA
I'm adding your collective stories to my list of reasons why I like my older, simpler furnace better. Still haven't bothered lighting the pilot light yet. Hasn't gotten cold enough in Baltimore yet (normally do that sometime in November).
 

mrsilv04

Thread starter
Messages
9,117
Location
Illinois
Originally Posted By: zzyzzx
I'm adding your collective stories to my list of reasons why I like my older, simpler furnace better. Still haven't bothered lighting the pilot light yet. Hasn't gotten cold enough in Baltimore yet (normally do that sometime in November).
This furnace was installed in August, 1996, and the replacement of the control board in January, 2014 was the first replacement part it had *ever* seen. You're somehow singling out a furnace that went almost 20 years without having a single replacement part being installed? Really?
 
Messages
2,105
Location
Easton, PA
Originally Posted By: zzyzzx
I'm adding your collective stories to my list of reasons why I like my older, simpler furnace better. Still haven't bothered lighting the pilot light yet. Hasn't gotten cold enough in Baltimore yet (normally do that sometime in November).
Pilot lights blow out and slowly fill a room up with gas if the valve fails. Does that seem safer? This reminds me of ours, doesn't always happen but when it is really cold it sometime fails to light on the first try. You can hear it reset and try again. I can only assume since it sits in the cold garage it has something to do with the hot surface ignitor not getting hot quick enough. Never had an issue outside of that though.
 
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