Lennox Gas Furnace Problem


Old 02-20-05, 06:42 AM
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Question Lennox Gas Furnace Problem

We have a Lennox gas furnace; it was working fine until I went on a vacation for more than a month. Before I left, I set up the system at the lowest settings, which is 50-55. Now since I got back home, it has been giving me a trouble, when I turn the system on it starts as it should be, but it throws a cold air, so I opened the cover from the furnace to see what is the problem, well there is a blue color box (control box) that lights up then I hear the click and pilot flame comes out, that hits igniter (looks like a pin) and I see gas flame starts pumping the flame through the burners/tubes, but in couple of seconds it stops, meaning the gas flames disappears, I only hear a motor of some kind running, not the fan, but something runs continuously.

I called local dealer who said it could be a flame sensor that needs to be clean or it could be the blue box itself. I don't have a manual for this so I have no clue where is the flame sensor is located. I tried to clean the igniter, pilot and there is the 3rd pin I believe that could be a thermocouple, but it didn't make any difference. Please help if someone who knows or having a same condition, it is cold out there and I am concern about plumbing pipes going to explode
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Old 02-20-05, 08:58 AM
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That Lennox should have a diagnostic code light on it that will flash a code that corisponds to a legend on the panel.

How does the pilot light ? Is it acomplished via a spark??

The one downside of owning a Lennox is that if you find the problem you will more than likely still have to call a Lennox dealer to get the part for you. Lennox is one of the hardest for homeowners to get parts for.
Old 02-20-05, 09:55 AM
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Thanks for replying, The model # it says G23Q3/4 but also says on the duct that is extending from the furnace model C26-41-1. under the furnace there is a control box by Johnson controls G776RGD-2 IPI also says # 69J3601 and part # 4,931,975. The green color light comes on as soon as I turn the system on, that is the only light there from what i see and it is located on the this blue control box. There are many wires there, but one white wire connects to what i believe is the igniter (that i broke while cleaning ) then rubber tube is i believe is connected to the thermocouple and then the silver metal tube is for gas and it is the one connected to the pilot. I am wondering where the flame sensor is, because the service man said just clean the flame sensor and 85% of th time it works.

I went to the Lowes and Home Depot, they suggested to go to the near by plumbing supply, but they are closed.


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