Kenmore Burner will not light...I'm Cold!

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  #1  
Old 11-11-05, 09:30 AM
hdrichie
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Kenmore Burner will not light...I'm Cold!

Hi,
First post....Need a little help
I tried searching the boards to find an answer but came up empty.

The Burner on my 5yr old Kenmore furnace NTC6075FBA1 will not light.
I'm no professional but ill try to explain what happens.
I turn the thermostat on calling for heat...I see the heating element turn bright red and Pilot lights...few seconds later blower starts.The burner never ignites...just blows cold air.
This started happening last season and I would just turn the furnace off and back on and 9 times out of 10 the burner would light.....Now I cant get the burner to ignite at all.
So here are my questions: Is there anything I can do myself before calling a Technician? also, What should I expect to hear and/or pay if I do need to call a Tech?

Thanks in advance
 
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  #2  
Old 11-11-05, 03:35 PM
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You around?

What puzzles me is why the blower comes on. This should be activated by heat. There is one other thing that can activate these to come on when they normally don't and that is if it is stuck on high limit. But normally when it sticks on high limit, the blower just keeps running and won't shut off.

But who knows how they wired that Kenmore.

I would first check to see if yu have a disc that has two wires going to it. The disc is about the size of a dime. In the middle of a lot of these discs is a little red? colored pin that sticks out. By pushing down on that pin..if you hear it click, that means you have just reset the stuck high limit switch. These are located on the upper part of the heat exchanger area in the same compartment where the burner and ignitor controls are, inside the main panel of your furnace. If there is no discernable click sound, then it means that that was not the problem.

About the only other thing I can think of is that your furnace has a thermocouple device, like a flame sensor that is in the line of the pilot fire and it is not sensing fire. Either it is burned out and needs to be replaced, or it needs to be pulled out and cleaned up. If it is one of those flame sensors, instead, this is a most easy task. The flame sensor is a probe at the end of a single wire that heads into where the pilot and main burner tube go. They are ususally held in place with only one screw.

The difference between a thermocopuple and flame sensor is this: A thermocouple flame sensing device is a metal capillary tube that has a probe on the end. The one end is screwed into the gas valve. But the flame sensor is all electrical. It has a probe of about 3 inches that goes into the fire. The other end of the WIRE is plugged into the brain box or ignition control module.

Get back with me after you try to confirm things I have said in this post.
 

Last edited by mattison; 11-13-05 at 08:27 AM.
  #3  
Old 11-12-05, 11:33 AM
hdrichie
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Thanks for the advice.
I located the Limit switches...there are 2 dime size ones with 2 wires going to each and the red pin in the middle....i pushed down on them but they did not move and no noticable click. There was also one closer to the exaust fan Size of a nickel with 2 wires goin to it...but no button on it.I checked all the conections to these and looked fine.
As far as the flame sensor/thermocouple device, i'm not sure I completely understand which it is. It is connected to the gas valve with 2 blue wires..two seperate things heat up...One is a small thin rod above the other which is more of a loop....this loop heats up gas goes in and pilot is lit then the thinner single rod glows.Not sure if that explaons enough to know which type it is?
Anyways....I pulled it out and cleaned it up still no go on the main burner coming on.

Edit: I justed looked in a different post and saw your recommended site.
I see the flame sensor I have here Honeywell Q3400A Flame sensor
 
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Old 11-12-05, 03:52 PM
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What becomes of the pilot light? All you say is the burner does not come on, and the fan then blows. But does the pilot stay lit?, or does it go out right away, after you see it come on?
 
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Old 11-13-05, 08:31 AM
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If you have a smart valve on that furnace have a pro diagnose it. Those valves were not very smart at all and are a very common failure.
 
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Old 11-13-05, 09:29 AM
hdrichie
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Pilot stays lit.... even after blower starts.

Yes It does have the smart valve.....I am leaning toward that being the problem...I dont want to mess around with the gas valve..... I will try to replace the pilot assembly myself , If that dont work I will just have to get someone out here to look at it.
 
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Old 11-13-05, 09:46 AM
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Originally Posted by hdrichie
Pilot stays lit.... even after blower starts.

Yes It does have the smart valve.....I am leaning toward that being the problem...I dont want to mess around with the gas valve..... I will try to replace the pilot assembly myself , If that dont work I will just have to get someone out here to look at it.

For some reason, your furnace has not acknowledged (doesn't "know") that the pilot is on. Or, the gas valve is faulty. If the gas valve is good and the circuitry is allowing the gas valve to try to open, you should hear and feel a faint click. Run the furnace and put your finger tips on the gas valve near where the wires are (but dont' touch wires) and feel/carefully listen for a click that should occur within seconds of the pilot being lit.

If you don't, the trouble could be in the ignition control board, or......

IF you hear the click, yet no burner flame, you coud have rust in your pilot orifice at the end of the pilot tube in by the burner, like *I* had recently on a furnace. (I had the same symptom as yours).

Or, the trouble could be that there is a sensor next to the pilot tip that isn't acknowledging the pilot flame. Either a flame sensor or thermocouple.

Look and see if there is any kind of rod that the pilot flame is aiming at. It may have a probe that should be in the flame. You could either have a weak pilot causing the weak flame to barely miss contacting the flame sensor or thermocouple, or the pilot flame is low due to corrosion in the orifice, or the sensor is bad, or the gas valve is bad. Those would be my initial guesses.

But look at your pilot when you run it to see if some of what I said might be going on here.
 
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Old 11-13-05, 10:40 AM
hdrichie
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Bonehead..I want to first say thanks for your help!

Here is what Just happened. I had the T-stat calling for heat...with the furnace shut off down stairs.I went down there opened it up so I could watch the pilot and listen. I turned on the furnace I heard a click... igniter lit up and pilot lit (pretty large pilot flame). The probe (which must be the flame sensor) is in the direct path of the flame and does glow after a few seconds.

I turned off the furnace again and then back on .....Pilot lit again then I heard the other slight click you mentioned and boom! main burners lit and I'm gettin heat Shut it off again then back on no main burner ...I did this several times and maybe half of the time did the main flame come on.
I would listen to the valve and I could tell when the burner would light by listening for that slight click....just not getting it everytime.
 
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Old 11-13-05, 12:31 PM
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Originally Posted by hdrichie
Bonehead..I want to first say thanks for your help!

Here is what Just happened. I had the T-stat calling for heat...with the furnace shut off down stairs.I went down there opened it up so I could watch the pilot and listen. I turned on the furnace I heard a click... igniter lit up and pilot lit (pretty large pilot flame). The probe (which must be the flame sensor) is in the direct path of the flame and does glow after a few seconds.

I turned off the furnace again and then back on .....Pilot lit again then I heard the other slight click you mentioned and boom! main burners lit and I'm gettin heat Shut it off again then back on no main burner ...I did this several times and maybe half of the time did the main flame come on.
I would listen to the valve and I could tell when the burner would light by listening for that slight click....just not getting it everytime.
Hmmmm. Thinking. You see...if it is a flame sensor, and all ELSE is well with the furnace, the burner flame will indeed come on everytime, if the set up is like most furnaces I am familiar with. If the flame sensor is faulty, the burner will stay lit for only about 4 seconds and go out. But with your issue, you don't even get the burner to try to come on, sometimes. AND, the sensor is in the pilot flame? Hmmm.

Tell me about that thing you think could be the flame sensor. Is there a wire or a small metal capillary tube that goes to it? If it is one small electrical wire, then it is some sort of flame sensor. And tell us if that probe is in the line of flame of the pilot or the burner flame. Which one? Then get back to us here.

Make sure that the terminals at the gas valve are tight, and not loose/tarnished. Shut off the furnace and pull off the terminals itf you can, and then reinstal, making sure they feel tight.

But if I were to be a betting man, I would say that that probe is not sensing the heat the way it should. Flame sensors can be polished up to be made to work, usually... but thermocouples don't work that way and need to be replaced. Thermocouples are screwed into the gas valve, like how the pilot line is screwed into the gas valve. If it's a thermocouple, I have seen the nut at the end at the gas valve where the line goes in, just loose enough to create bad contact. You never want to overtighten these though. Always use a small wrench to tighten them as to not create too much leverage. Just snug it.
 
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