Lennox G24M NG Furnace not lighting.


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Old 11-15-09, 12:41 PM
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Lennox G24M NG Furnace not lighting.

My gas furnace is not lighting. It is sequencing through the draft fan and then you hear a click and the gas valve opens and then it closes without the ignitor trying to light it, it then reopens the gas valve and closes without attempting to light the gas. It goes through this sequence 5 times or so and then stops.

The gas valve is sequencing at the same rate that both LED's are flashing, at this point I am leaning toward replacing the board but I would like to make sure first.
 
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Old 11-15-09, 12:57 PM
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Is the hot surface ignitor heating up to being white hot before the gas valve turns on?

If not, remove the HSI and inspect it for cracks.
 
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Old 11-15-09, 01:11 PM
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I agree, inspect the hot surface ignitor.

 
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Old 11-15-09, 01:12 PM
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When it did light yesterday you could hear the spark of the ignitor so I am not sure that it has an HSI. I am more used to working on big comercial units, but the HSI just glows it would not click light a spark ignitor correct???
 
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Old 11-15-09, 01:42 PM
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It's odd that Lennox made a spark ignition and an HSI G24M furnace in the same year. If you do replace your board be aware that they tend to be kits unlike the original.

They do some strange things like put a humidifier terminal where a ground terminal was on the old board.

What LED code is diplayed when ignition fails?
 
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Old 11-15-09, 02:08 PM
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Here is a manual on the G24 furnace, which specifies an ignitor.

http://www.lennox.com/pdfs/manuals/L...0%20Manual.pdf


There are different series of this equipment, which has a letter in addition to the model. Do you have a G24M series, for example?


Of course, if you have an intermittent pilot ignition system, you need to deal with that rather than whatever a manual I might dig up suggests.

But I'd double check and verify what king of ignition system you have. Listening for clicks doesn't really cut it either.

Do you know what to look for?
 
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Old 11-15-09, 02:12 PM
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I took out the burner assembly and verified that it does have a spark ignitor, with no obvious problems with the ignitor.

There are no codes flashing both LED's are flashing simultaneously in rhythm with the gas valve cycling.

I am leaning toward replacing the board because it acts like it gets to the part of the cycle where it opens the gas valve and just stops. It doesn't seam like it is looking for heat or anything beyond the gas valve opening.
 
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Old 11-15-09, 02:31 PM
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This is the spark ignition manual...
http://tech.lennoxintl.com/PDFs/503321.pdf
 
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Old 11-15-09, 02:58 PM
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The diagnostic codes for the ignition control are detailed on pages 23-24 of the manual posted by Houston.

What codes are you being given?
 
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Old 11-15-09, 04:00 PM
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As stated earlier I am not getting any of those codes. I did find some helpful information on an earler posting from Jan 09, I took a hairdryer out and put it on the card while it was cycling. After 3 or four cycles the valve stayed open and continued its cycle and lit the burner and the furnace is still running. I will take my meter and out and see if I am getting the correct voltage on the gas valve or if my relay is getting weak.
 
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Old 11-15-09, 08:48 PM
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Frankly, I find your description of the operation of your furnace to be unhelpful in trying to identify what the problem might be.

If you aren't getting any of the diagnostic codes listed, you have problems, since you should be getting a slow flash when the power is on and no call for heat and a fast flash when there is a call for heat.

So I'd encourage you not to draw conclusions about what is happening, but to describe what is happening, and start again.

In particular, there is a good description of the furnace sequence of operation on page 23. Follow that and tell us how far you get and where you wind up on that chart.
 
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Old 11-16-09, 05:42 PM
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Frankly I find your attitude to be very condescending, you have no idea who you are talking to on these forums and you seem to be full of yourself.
 
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Old 11-16-09, 06:04 PM
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Has the furnace already ran this year?, to know that the line is more likely full of gas, and not some gas issue? Do you have other gas appliances that work?

You can look at say the 1/4 or 1/2 foot dial on your gas meter to see if everytime you hear the click of the gas valve open for up to 5 seconds, during sparking, that some gas is being released. (Unnecessary of course if you can smell it.)

Maybe spark is not jumping to where it should? It may be leaking out the sparkplug-like wire or something, and that is where you hear the spark. Or it may have partial/weak spark due to partial spark/short in the ignition control. See what you can see in the dark, and see if blue spark where it should be at electrode. Make sure ignition contol box, if you have one, and if it has a metal plate behind it, that it is grounded good. Loosen and retighten mounting screws to be sure.

Note: Spark + gas at proper location for both should = fire. And it should not even get to the spark stage if say you had a drafting issue, so that kind of rules out poor drafting, as an issue.

..........................................................

Oh. And maybe SP was hoping yesterday, that New England would win, and you caught him at the wrong time.
 

Last edited by ecman51; 11-16-09 at 06:13 PM. Reason: Added more
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Old 11-16-09, 06:11 PM
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Thanks for the help but my problem is solved.
 
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Old 11-16-09, 06:17 PM
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What was it? And did you solve it yourself?
 
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Old 11-16-09, 06:23 PM
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Yes I fixed it myself, it was the circuit board which is exactly what I figured it was from the start. I just got on this forum to see if I could get any help to make sure that I was correct before I spent $200 dollars on a new board.
 
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Old 11-17-09, 06:51 AM
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It can be fairly common to have circuit boards go out in any appliance.

But due to their cost, if one values their money, one needs to eliminate all the other possiblies you can test for, since with circuit boards, their are no really good tests other than as stated - the process of elimination.

None of us here want to jump the gun, and get someone to replace their circuit board and have them come back here and say that was not it.
 
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Old 11-17-09, 08:27 AM
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Originally Posted by Terry4336
Frankly I find your attitude to be very condescending, you have no idea who you are talking to on these forums and you seem to be full of yourself.


Well, Houston and I both concluded from your initial post that you had a hot surface ignition system. Your remarks were unclear to the point of being able to deceive both he and I. That applied to some subsequent posts as well.

You displayed what I would describe as the unorganized and scattershot approach to troubleshooting characteristic of DIYers. That's not being critical, it's the nature of not having a reliable method of diagnosing problems in equipment of this kind.

What those of us offering advice can offer the most is a more logical means of analyzing problems than most DIYers can come up with on their own. You remained proudly independent of following that kind of approach in every one of your posts, so far as I can see.

Be that as it may, you apparently solved your problem on your own. I don't see that you benefitted at all by the attempts of others to help you here. Congratulations on your success --- it's entirely your own.
 
 

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