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Old 12-10-2008, 11:48 PM   #1
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Lennox furnace problem


I am having a strange problem, which started happening the last few days with my Lennox furnace. Occasionally the furnace flames will kick on for about 5 seconds and then kick off before the blower gets a chance to start. The system will keep retrying to startup by re-igniting the flame about every 60 seconds, but once again after 5 seconds after the flames start they shutdown again... Any advice would be appreciated.

devgill08

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Old 12-11-2008, 12:54 AM   #2
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Lennox furnace problem


I'm going to assume you have a 80-90% gas furnace, so here goes. In your row of burners there should be on the left side a wire lead going to what will look to be a ceramic tube with a little steel rod coming out of it at an angle across the burner. This is a flame sensor. Its attached to the burner assembly with a 1/4" screw (nut driver will work best), remove screw and flame sensor. Clean metal rod with a slightly abrasive cloth (purpose is to remove any blackness or charring). Reinstall flame sensor, reset furnace switch and see if the burners will stay light longer than 3 seconds.

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Old 12-11-2008, 01:11 AM   #3
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Quote:
Originally Posted by jsnova View Post
I'm going to assume you have a 80-90% gas furnace, so here goes. In your row of burners there should be on the left side a wire lead going to what will look to be a ceramic tube with a little steel rod coming out of it at an angle across the burner. This is a flame sensor. Its attached to the burner assembly with a 1/4" screw (nut driver will work best), remove screw and flame sensor. Clean metal rod with a slightly abrasive cloth (purpose is to remove any blackness or charring). Reinstall flame sensor, reset furnace switch and see if the burners will stay light longer than 3 seconds.
ok where is the Flame sensor in this picture thank you
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Old 12-11-2008, 01:39 AM   #4
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Lennox furnace problem


okay you have a Lennox G26 furnace. The nice thing is that everything is 1/4" screws. On the higher part of the furnace there are five screws on the burner box front. There should also be 2 on the underside of the burner box. Remove the 5 front screws and loosen the bottom 2. With two hands pull at the door so it comes loose from the bottom screws, then remove the door. You'll now see the burner assembly. Look at the gas line manifold that attaches to the burners. Follow it down to 2 screws on the right. Remove em. Pull down slowly on the manifold, be careful to watch the black vacuum lines (make sure if you pull em apart, you put them back together). If you look underneath the burners, you'll see 2 screws attaching the burners to angles on the box wall. Remove those 2 screws, then carefully slide out burner assembly. The flame sensor is on the top left. Be careful with your ignitor, its on the right side. Clean your flame sensor, and while you're at it, check the carryover slits between the burners for rust or obstructions. While you're at it you mind as well clean your burners. If you do, remove the ignitor from the burners, you don't want to scratch it. Cleaning burners is best done with a wirebrush.

Everything after the "remove the burners" part is up to you. Just figured while you have it out, and if you've never cleaned them, its a good time to. Your furnace is more than likely at least 5 yrs old. Put it all back together and make sure the burners sit ON TOP OF those little angle pieces. Also make sure the semicircle piece of rubber that is attached to the flame sensor gets put back in place on bottom of burner box with ignitor wires.

And just to let you know, if a pro did this, you'd prob be spending $200+.
Good luck!
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Old 12-11-2008, 12:20 PM   #5
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Quote:
Originally Posted by jsnova View Post
okay you have a Lennox G26 furnace. The nice thing is that everything is 1/4" screws. On the higher part of the furnace there are five screws on the burner box front. There should also be 2 on the underside of the burner box. Remove the 5 front screws and loosen the bottom 2. With two hands pull at the door so it comes loose from the bottom screws, then remove the door. You'll now see the burner assembly. Look at the gas line manifold that attaches to the burners. Follow it down to 2 screws on the right. Remove em. Pull down slowly on the manifold, be careful to watch the black vacuum lines (make sure if you pull em apart, you put them back together). If you look underneath the burners, you'll see 2 screws attaching the burners to angles on the box wall. Remove those 2 screws, then carefully slide out burner assembly. The flame sensor is on the top left. Be careful with your ignitor, its on the right side. Clean your flame sensor, and while you're at it, check the carryover slits between the burners for rust or obstructions. While you're at it you mind as well clean your burners. If you do, remove the ignitor from the burners, you don't want to scratch it. Cleaning burners is best done with a wirebrush.

Everything after the "remove the burners" part is up to you. Just figured while you have it out, and if you've never cleaned them, its a good time to. Your furnace is more than likely at least 5 yrs old. Put it all back together and make sure the burners sit ON TOP OF those little angle pieces. Also make sure the semicircle piece of rubber that is attached to the flame sensor gets put back in place on bottom of burner box with ignitor wires.

And just to let you know, if a pro did this, you'd prob be spending $200+.
Good luck!
Hi Jsnova,


ok I found 3 problems ……………………………..

(1) Low 3A batteries …………………………not yet install it will be install tonight
(2) Out side vent also blocked by frozen ice only less than half open………………………….. Its cleaned now
(3) Hose( Lift to right) under the combustion motor that goes lift to right inside under the combustion air and than this hose comes out back off the furnace & goes into basement floor drain……. …………………when I took it out blow the air with mouth water came out all the way to floor drain and it opened up it was blocked bad I think this was the problem

Good news.

After putting clean Hose back( Lift to right) under the combustion air blower motor all together now its working fine and thank you again helping me out on my hardship


devgill08…………………… says thank you
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Old 12-11-2008, 08:38 PM   #6
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Lennox furnace problem


Take the black hose that drains the rubber boot on the left side and runs into the condensate trap on the right side off and flush it ONCE A YEAR with hot water in your sink. Make sure the white barbed fitting where it attaches to the rubber boot is clear also. Cinch up the hose onto the boot with a tie wrap/zip tie if it leaks.

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