# Ignition failure in furnace



## HilltopDaisy (Feb 26, 2003)

I have a Coleman propane furnace in my home (trailer), the furnace is 5 years old. I have no heat this morning, and the diagnostic flashing green light is telling me that it has "ignition failure". Anyone know if I could try to fix this myself? Thanks.


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## justmyluk (Apr 28, 2005)

I know this may be a dumb question...But did you check to see if you had propane???


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## OkieDavid (Jan 15, 2007)

Sorry I'm not familiar with your heater but in the interest of trying to get you some heat this morning I'll give it a shot. Does it use a pilot light or is it an electrical ignitor? If electrical check for some reset button since with the light flashing it appears to have power going to the unit. If it's pilot light controlled, you probably just need to heat up the thermocouple with a match/lighter (manually light the pilot).


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## marvella (Oct 12, 2003)

i'd say thermocoupler too.when you try to light it, it lights but wont stay lit, that's probably it.


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## HilltopDaisy (Feb 26, 2003)

Yep, got plenty of propane. The owners manual says it will attempt to fire up once per hour if the ignition fails, which it has been doing. The first 2 times it just cut out at the point when it didn't light up. This time it went all the way to the blower coming on, but it's blowing cold air.

I called a repaiman and he said it could be 2 or 3 different things. He's able to come out this morning, so that's what I've decided to do. I'll watch him closely and see what I can learn. Thanks for your help.


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## Highground (Jan 22, 2003)

No kerosene heater as backup?


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## sawdon65 (Dec 13, 2005)

Everytime that has happened to me its been the thermocoupler...


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## fishhead (Jul 19, 2006)

The day before I was leaving for a couple of days my furnance would start, run a minute and then shut down.

It's a high efficiency furnace and it turned out to be fly pupae plugging the condensation drip line. Of course while I was messing with it I fried a $.30 fuse so I had to drive an hour to town and back.


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## crafty2002 (Aug 23, 2006)

HilltopDaisy said:


> Yep, got plenty of propane. The owners manual says it will attempt to fire up once per hour if the ignition fails, which it has been doing. The first 2 times it just cut out at the point when it didn't light up. This time it went all the way to the blower coming on, but it's blowing cold air.
> 
> I called a repaiman and he said it could be 2 or 3 different things. He's able to come out this morning, so that's what I've decided to do. I'll watch him closely and see what I can learn. Thanks for your help.


I think that was the best thing to do even if it breaks the bank. Heaters can be dangerous as all get out when someone that doesn't know how to fix them tries. Especially Propane. Hopefully it isn't much, but whatever is cost it's better than being out side in the cold without a roof. 
IMHO 
Dennis


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## tamsam (May 12, 2006)

Although we have wood and a propane space heater for backup we also have 2 kero portable heaters, one big and one small. You never know when you may be stuck in and if you are sick or whatever reason you can't get wood in. Sofar this year we haven't fired up the kero and hope we don't need them. Everyone needs a back up. Sam


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## hunter63 (Jan 4, 2005)

So, what was the problem, if you mind my asking?


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## ColumbiaSC. (Nov 25, 2005)

thermocoupler would be my guess, the tip burns out and it tells the furnace controll switch to stop sending the gas to make the fire to heat the house! This is not a hard replacement part but it does take a little simple smarts. 
a screw driver and a 1/4" nut driver worked for me. I had to remove the viewing cover, mine was round with the veiwng window in the center. 
The replacement part came rolled in a circle with a nub tip on one end and a threaded tip on the other, I rememberd how it looked and replaced the old one with the new one in about 2 mins after opening up the front of the furnace ( round check window part). This is not at all hard, the nub rounded end is about a 1/4" in size wide and about 1 1/2" long end sets under the pilot lights flame. They come in different lengths so before you buy one kinda look at it and guess about how long it is.. 16"-24" or more or less " , I could be off here. If you have ever lit a pilot light you have unknowingly seen it. Just look how the old one is in there and replace it with the new one. You can do this. But be careful as always.


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## WayneR (Mar 26, 2007)

Daisy,

Is your furnace a high efficiency model? If so, a common failure is the carbide ignitor that starts the gas burning. If the ignitor fails the unit will cut off as a safety feature.


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## Michael Kawalek (Jun 21, 2007)

That's what happened to my home furnace. I could hear the gas start to flow but it was quickly shut off when it didn't ignite. The igniter was a bad glow plug that wouldn't get red hot. It had collected ashy debris over the years and short circuited. I made the mistake of cleaning it with a wire brush. I started out with an old toothbrush and it cleaned up OK. I decided though that wasn't good enough and tried a wire brush. The glow plug was ceramic and it broke once I hit it with the wire brush. After I went to the store and bought a new plug it got red hot on the first try and the lit the gas immediately.

That sounds like what is happening here. If the propane is set afire electricaly, then the lighting element is not working. Try brushing it clean first, and it that doesn't work, than replace it.
Michael


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## hunter63 (Jan 4, 2005)

I was asking the original poster if the service guy had been there and what he found.
It is important to know have type of furnace you have, even when calling the service guy.
Even though it is good advice on a LOT of furnaces and water heaters, the 1st thing I always see on questions like this is,"change the thermocouple(r)".
Fact is that if it's newer it probably doesn't have one.

Thermocouples are used on a "standing pilot" type ignition.
The thermocouple generates 30 Mv of electricity to hold the "pilot valve" portion of the gas valve, insuring that there is indeed a flame,(safety, as well as operational), that will ignite the gas when a call for heat is present.

There are also, a "spark to pilot", in which a call for heat starts the spark-er, sparking, then igniting the pilot, which in turn opens the "pilot valve",heating the thermocouple, same reason as the standing pilot, but doesnt require the pilot to burn continuously, making the unit more energy efficient.
In both cases the thermocouple is a good place to start in trouble shooting.

Newer and higher efficiency furnaces some times use a "Hot Surface Ignitor", (HSI), or glow plug, glow bar etc. These mostly have a "flame sensor" located on the opposite side of the burner lay out, from the HSI. This does the same thing as the thermocouple, prove that there is a flame, and allows the main gas valve to open.

Trouble shooting tip, this "flame sensor" gets dirty and will not allow the gas valve to open. Clean with steel wool, brass brush, sandpaper.

There are usally several other components involved with the efficiency furnaces, such as induced draft motor/blowers (blows air into the combustion area), or vent motor/blower, (sucks hot gas out and vents outside).
Either or generally uses a pressure or a vacuum switch to insure that the motors/blowers are in dead running and are clear of obstruction.
Add a couple of limit switches, ie. High limit, flame roll out and a circirt board (for ignition, blower control times etc.) there are all sorts of stuff that will not let it run.
As it is cold here, I just hope it got fixed.


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## WayneR (Mar 26, 2007)

The carbide ignitors (in whatever form) are extremely fragile! A visual examination may not reveal a problem with them. As they are subjected to thermal shocks, hairline cracks in them are common. If inclined, they can be tested for continuity and operation 'out of circuit' .

If your furnace uses one of these, get a spare now, as it is a question of when not if, it will fail.


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