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Furnace flame doensn't stay lit

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  • Oct 9th, 2019 10:59 pm
[OP]
Deal Addict
Apr 18, 2013
3206 posts
1368 upvotes
Canada

Furnace flame doensn't stay lit

This morning my furnace started cycling on and off. Different from the last time. This time, the flames inside the furnace will light up for only around 20-30 seconds, then shut down. Then the furnace tries again. It did this probably a dozen times this morning. I changed the filter, and the same problem continued. Then about an hour later, the furnace started working normal and ran for about an hour. But now it is back to doing the same cycling and the flames shut down after 20-30 seconds. The furnace is giving me a code 34 which is something to do with the ignition, but could be a number of things. The furnace was recently cleaned and inspected in April 2019 and is in otherwise very good shape.

I did some quick research and think it might be the thermocouple either needs to be replaced or adjusted.

Thoughts?
40 replies
[OP]
Deal Addict
Apr 18, 2013
3206 posts
1368 upvotes
Canada
DaveTheDude wrote: You can try cleaning your flame sensor.

The flame sensor was cleaned this past April and was deemed to be in good condition.
Member
Mar 11, 2019
303 posts
177 upvotes
open all the air registers / grills.
[OP]
Deal Addict
Apr 18, 2013
3206 posts
1368 upvotes
Canada
jintau wrote: open all the air registers / grills.
They are all open.
[OP]
Deal Addict
Apr 18, 2013
3206 posts
1368 upvotes
Canada
One question: Is the flame sensor different than the thermocouple? Does my furnace have both? It's a 2002 Bryant.
Member
Mar 11, 2019
303 posts
177 upvotes
gbill2004 wrote: One question: Is the flame sensor different than the thermocouple? Does my furnace have both? It's a 2002 Bryant.
Yes its different, no there wont be both. doesn't sound like a DIY to me as long as the air grilles are all open and air is coming out.
Deal Addict
Feb 25, 2007
2473 posts
354 upvotes
is the water drain clogged (or whatever you call it)? happen to me before, Lennox, You have to clear the clog, otherwise the water goes back into the unit, so it shuts down, so it cycles.
[OP]
Deal Addict
Apr 18, 2013
3206 posts
1368 upvotes
Canada
rogerrabbit168 wrote: is the water drain clogged (or whatever you call it)? happen to me before, Lennox, You have to clear the clog, otherwise the water goes back into the unit, so it shuts down, so it cycles.
I'm not sure. How would I know if it is clogged and how do I unclog it?
Deal Addict
Mar 3, 2018
1529 posts
1464 upvotes
GTA
Bryant and Carrier as in the video above are made by the same company. Also just because a furnace service says they did something doesn’t mean they did it. Unless you were watching.
Deal Guru
User avatar
Feb 11, 2007
14655 posts
15441 upvotes
Oakville
gbill2004 wrote: The flame sensor was cleaned this past April and was deemed to be in good condition.
Maybe they didn't actually clean it, or maybe they moved it out of position, or maybe they damaged it?
[OP]
Deal Addict
Apr 18, 2013
3206 posts
1368 upvotes
Canada
engineered wrote: Maybe they didn't actually clean it, or maybe they moved it out of position, or maybe they damaged it?
Well I was there watching the tech and he didn't do anything unusual.
[OP]
Deal Addict
Apr 18, 2013
3206 posts
1368 upvotes
Canada
DaveTheDude wrote: Bryant and Carrier as in the video above are made by the same company. Also just because a furnace service says they did something doesn’t mean they did it. Unless you were watching.
I was standing there watching the tech the entire time.
Jr. Member
Feb 28, 2018
144 posts
88 upvotes
Waterloo region
if it was the flame sensor (flame failure) the furnace would lock out after 3 retries. it would need to be reset.. it sounds more like its cycling on the pressure switch , which would be related to the vent being partially blocked, or the drain is plugged... probably more likely to be the drain..
Deal Guru
User avatar
Feb 11, 2007
14655 posts
15441 upvotes
Oakville
gbill2004 wrote: Well I was there watching the tech and he didn't do anything unusual.
Are you technical enough to know what he is doing? Otherwise why not do it yourself?
Not saying the tech did anything wrong on purpose, but stuff happens.
If he did just service, does he not provide some warranty? Otherwise what's the point of the service?

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