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Old 01-10-2010, 08:43 PM   #1
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Furnace problems...


Model # NUG9100FHB1
it is a high efficency furnace.

There are four burners (inshot type), I have cleaned all the burners at the front I can get a dime just to start in the opening. My pilot comes on, it is not plugged, when the pilot comes on and the burners ignite the furnace hammers hard...the furnace is located in the basement and I can hear it loudly and feel it bang all the way upstairs.

I have tried adjusting the pilot for less and more pressure and that doesnt help. The problem is intermitten it comes and goes, more so there then not but sometimes it doesnt bang...does anyone know what might be the problem and how to fix it? My fresh air or intake is not obstructed.

Thank you in advance for any help you can provide.


Last edited by Jay0018; 01-10-2010 at 09:04 PM. Reason: more information
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Old 01-10-2010, 09:15 PM   #2
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Furnace problems...


is flame rolling out front of furnace when it fires up? are burners properly installed?furnace might be filling with gas before lighting off

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Old 01-10-2010, 09:32 PM   #3
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If I understand your post correctly , yes with the burner cover off the flame does roll out sometimes other times it does not but still hammers hard.The burner assy should be I put it back together the same way I took it apart,far as I know you can't put it in wrong otherwise my ignitor assy and pilot would not hook up to burner assy.

If it helps any the house was vacant for a year before I bought it. My boss does heating and cooling on the side and we have had the thing apart several times cleaning it and the problem is still there. I have no special equipment or meters to test anything, just hoping someone could give me an idea that we haven't tried yet.

That does seem to be the problem as you mentioned the pilot does not seem to be igniting the burners quick enough,although at times it has lit the burners with just a little puff which is acceptable to me then it goes back to hammering the next time it cycles???
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Old 01-10-2010, 09:39 PM   #4
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Furnace problems...


Did you check the heat exchanger yet? Gas valve closing on shut down and not allowing seepage into the chambers between cycles?
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Old 01-10-2010, 09:41 PM   #5
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ive seen furnaces where pilot light assem was reinstalled under burner area instead of over it causing furnace to fill with gas before reaching pilot,im here to tell youit will get your attention! im guessing there is bar/tube across front of burners that guides gas from burners to pilot to light them off,is it clean?also have you checked heat exchanger for cracks while burners were out ,could be sucking extra air into furnace?
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Old 01-10-2010, 09:58 PM   #6
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Here is pics of it if it helps any, as far as I know there are no cracks in the heat exchanger. Yes gas valve is closing on shut down, it is turning the burners off and with the burner covers off there is no smell of gas, i think that if the gas valve wasnt closing you would be able to smell the gas coming from the furnace?...





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Old 01-10-2010, 10:13 PM   #7
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Hard to tell by a picture but why is there red in the third cell from the right ? The burn on the far left doesn't look correct either. I'm thinking heat exchanger cracked. Have it checked out by a qualified tech tomorrow.
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Old 01-11-2010, 12:42 AM   #8
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Thanks for all the feedback guys appreciate your input . Call us crazy but had my boss come out and we did more troubleshooting disconnected the ignitor from the burner assy. using a torch we kept that lit at the burners with the pilot and ignitor assy. outside the furnace , called for heat and the burners lit and the pilot didn't come on until about 3 seconds after the burners lit so thinking it might be a faulty circut board?. My understanding from what people have told me is that it's probably not a bad gas valve they either work or they don't there is no grey area is that correct?.

Yes it's just the pic I have a nice blue flame on all 4 cells there is no red when furnace is on so we are pretty sure heat exchanger is not cracked.Any feedback on the new trouble shooting listed will be appreciated.
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Old 01-11-2010, 02:10 PM   #9
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Figure I would update everyone that offered input.I put the pilot assy back together last night after my boss helped with the trouble shooting as stated in the previous post then took the lower cover off to check out the bottom half which just has the blower and circut board.

The key here I think, is as I stated in a earlier reply is that the house sat vacant for atleast a year if not more. I wiggled all the stakeon connections on the circut board and the plastic connection going to the ignitor and pilot assy. The furnace has been firing up fine every time no more hammering during ignition!

So not knowing anything about this stuff withhout proper test equipment my guess is that I had corrosion build up on connectors from sitting so long or there is a short somewhere and the jiggling of the wires helped.

All I know is that I just saved myself atleast $500.00 to $1000.00 dollar bill this time of year to have a tech come out to the house just to tell me it was corrosion or a short.
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Old 01-11-2010, 03:19 PM   #10
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Nah.

I come out and tell customers that for a lot less then 500 bucks.

About $125.00 for that, and I would have cleaned up all the connections. And replaced any bad stay conns.
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Old 01-12-2010, 01:55 AM   #11
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Well beenthere your one of the few honest people out there in the world, no disrespect intended to anyone. As my boss stated today the tech he talks to said "to be honest with you I would have chalked it up to a bad board and replaced it".
Most places here in Michigan want 100 bucks just to drive out to your home around 200.00 for the circutboard from what I was told that's their cost so you know there is going to be a mark up on that to the customer then another 85.00 an hour for labor if not more.

I won't mess with it now since the furnace is working fine still , but come warmer weather I will put a little dab of dielectric grease on each of the connections on the circutboard to prevent the problem in the future.

Thanks again for all the help and feedback from everyone.
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Old 01-12-2010, 02:35 AM   #12
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Furnace problems...


any diff with burner cover door on/off
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Old 01-12-2010, 05:25 AM   #13
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Quote:
Originally Posted by Jay0018 View Post
Well beenthere your one of the few honest people out there in the world, no disrespect intended to anyone. As my boss stated today the tech he talks to said "to be honest with you I would have chalked it up to a bad board and replaced it".
I charge a good fee to tell you what is wrong. If you decide to let me fix it.
On dirty connections, I'll waive the diagnostic fee. And just do a labor charge.

Now, on the other hand. if it were the board. I get a good amount for the board and labor to change it. And I don't waive the diagnostic.

There are techs that like to fix things. Which means they investigate what is actually causing the problem.
Then, there are techs that just put on parts, and hope they are right, because that is all they know. They haven't been taught how to trouble shoot/investigate for cause.
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Old 01-13-2010, 01:11 AM   #14
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Quote:
Originally Posted by kennzz05 View Post
any diff with burner cover door on/off
If your asking if I have tried it since the problem has been fixed , no I haven't but I could if that is what you are asking.
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Old 01-13-2010, 01:25 AM   #15
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Quote:
Originally Posted by beenthere View Post
There are techs that like to fix things. Which means they investigate what is actually causing the problem.
Then, there are techs that just put on parts, and hope they are right, because that is all they know. They haven't been taught how to trouble shoot/investigate for cause.

Agree with you , doesn't matter what the feild is see it at the machine shop I work at we have several machinest that never investigate or trouble shoot the actual cause of any given problem.

I blame myself for not giving enough information in my original post asking for help when a few said that my heat exchanger was bad, I didn't feel that was the root cause of my problem because the hammering was intermitten it would come and go.

I will admit though that since I don't really know squat about heating and cooling I did ask about it and was told that it was possible but not likely based on it being an intermitten problem.

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