HVAC guru's need help

[buelliganx1]

So I've got a Lennox high efficiency gas furnace that has had an issue that I've been fighting for a while. Well actually when I first bought this house we had the problem then my brother in law cleaned some things and it seemed to be working well but now it's doing it again.

The problem is the burner will not stay lit but it will stay lit if I simply take the cover to the blower off. With the cover on you can hear the ignition firing then see the pilot light then the burner fires up but after maybe 5 seconds the burner goes out again. If I take the cover to the burner off it's the same sequence but the burner stays lit, if I put the cover back on as soon as I put it on you can see the burner flame turn from blue to orange then back to blue again then about 15-20 seconds later the flame goes out again. With this coming weeks frigged temps this is really starting to worry me.

Thanks and any advice would really be appreciated.

[Duff1647545513]

Try cleaning the flame sensor. It kinda looks like a little pin sticking up where the flames can hit it.

 

If he had cleaned stuff and it was working fine for awhile, there's a chance the flame sensor got dirty again, sometimes it takes a few years between cleanings. There are tons of YouTube videos if you want a visual on how to do it

[Green Bastard]

Edit, what he said ^.

[buelliganx1]

I thought about that and I will try it but why would it work fine with the burner cover off of the sensor was dirty?

[XChris1632X]

Like said above try flame sensor first.

 

If that doesn't work you may have a pressure issue. it could be that it is tripping the switch when you put the cover on. Is it 90% efficient furnace with plastic flue pipes? I know you said high efficiency but 30 years ago the high efficiency furnaces were not 90%.

 

If it is and the problem continues, start with the fresh air pipe and make sure nothing is clogging it or blocking the exit. Then move to the exhaust and do the same. Some times a faulty pressure switch can be the culprit as well.

[buelliganx1]

Yes it's new enough that it has the plastic flue pipes going out of the side of the house.

What pressure switch are you referring to? Is there something that measures the pressure inside of the burner box?

[buelliganx1]

Well knock on wood but I think I fixed my problem. I checked out my fresh air pipe and it was clean from the furnace out then I took a close look at the screen that sits above my burners just below my intake pipe and found two small dried up leaves blocking the airway. Now keep in mind that this screen is probably at least 14"x 10" since it covers all of the burners and the fresh air pipe is probably a 6" pipe, could these little shriveled up leaves really impede airflow so much that it would cause me problems? I removed the leaves and things are working as advertised right now, hopefully it continues to do so.

Thanks for all the help.

[MattKatz]

Doubtful hat would cause an issue, However you need to give us more info on what you are working on , specifically the Ignition start style would be very helpful to me.

[buelliganx1]

Well it's a Leeno model number G26Q4/5-100-1

Its got a spark ignition, just a little wire that arcs a spark to start the pilot light.

[lag wagon]

If it goes out again, check the diagnostic lights (for real, it should have 1 or 2 LEDs that will blink)

[buelliganx1]

Are the lights under the lower panel? I've never seen any lights while poking around on this thing.

[cstmg8]

Are the lights under the lower panel? I've never seen any lights while poking around on this thing.

 

They are usually behind the lower panel, but there is also usually a small window where the flashing can be seen.

[buelliganx1]

Hmm I'll have to check that out.

[acklac7]

Doubtful hat would cause an issue, However you need to give us more info on what you are working on , specifically the Ignition start style would be very helpful to me.

 

I thought you were done giving advice

 

(Kyle helped me trouble shoot my AC a couple years ago, had the problem diagnosed in under 20min, saved me countless $$$...thanks again)

[buelliganx1]

I thought you were done giving advice

 

(Kyle helped me trouble shoot my AC a couple years ago, had the problem diagnosed in under 20min, saved me countless $$$...thanks again)

 

+1000 thanks if he can pull that rabbit out of his hat again.

[buelliganx1]

I thought you were done giving advice

 

(Kyle helped me trouble shoot my AC a couple years ago, had the problem diagnosed in under 20min, saved me countless $$$...thanks again)

 

And I'm with him I don't think that those leaves should have caused a problem either.

[Big Chief2011647545501]

I had a similar problem when the weather started to get cold. I cleaned the sensor but that didnt fix my problem. The heartbeat light was 2 quick flashes then none so it meant that it wasnt lighting. I cleaned the screens where the gas comes out the pipes to the burners and that did the trick. Give it a shot.