Coleman furnace won't ignite

Problems related to residential installations.

Coleman furnace won't ignite

Postby capablewoman » Mon Nov 04, 2013 11:30 am

I have a 2002 Coleman furnace model number GM9S100C6UP11G that wasn't throwing any heat but the fan was running. The blink code was 7, which indicated a lockout due to three tries for heat. On inspection I noticed that the HSI was cracked, so I replaced that, and I also cleaned the heat sensing rod to be safe, as that looked to be in good shape. The call for heat sequence works fine, the gas tries to ignite on the HSI but the gas won't stay on long enough to ignite the chamber. However, when I pulled the chamber cover off and turned the furnace back on, it lights just fine and I can replace the chamber cover and it keeps heating. Does this mean I don't have enough gas pressure?
capablewoman
New Contributor
 
Posts: 5
Joined: Wed Oct 30, 2013 3:20 pm

- Coleman furnace won't ignite

Postby Freon » Mon Nov 04, 2013 5:45 pm

"when I pulled the chamber cover off and turned the furnace back on, it lights just fine "

Pulling the cover off lets in more air (oxygen) so you should make sure all vents/openings into the combustion chamber are clear.

The lack if timely ignition could also be an improperly located/installed hot surface ignitor (HSI)... or the wrong one. I assume you bought the EXACT HSI as was there before. Check it's location relative to the burner gas jets. Check the gas jets for any rust and/or other blockage keeping the gas from the HSI.
Freon
Most Valued Contributor
 
Posts: 715
Joined: Sat Jun 18, 2011 11:26 am

- Coleman furnace won't ignite

Postby capablewoman » Mon Nov 04, 2013 7:39 pm

Thank you for your reply! I did purchase the exact matching brand and model of HSI, and it is installed in the only way it can be, in a cradle that screws into the combustion chamber. I will check the vents, as the thought did occur to me but I haven't looked closely for where it would be vented. I did wipe off all of the jets, thinking that might be the problem after the HSI was replaced and it still wasn't igniting. You can see the blue gas flame from the first jet on the call for heat both with the cover on and off, it just doesn't have enough "umph" to fire all of the jets when the cover is on. Is there a special way to clean the jets other than wiping a cloth over them?
capablewoman
New Contributor
 
Posts: 5
Joined: Wed Oct 30, 2013 3:20 pm

- Coleman furnace won't ignite

Postby Freon » Tue Nov 05, 2013 2:45 pm

Depending on the type of burner you can use a pin to make sure the wholes are clean. Be careful of a cloth because you may wipe crud into the opening. Not knowing the type of burner it's hard to say the best way to clean it,

Your wrote "... wasn't throwing any heat but the fan was running." Which fan are you referring to? Is it the draft inducer that starts before the HSI glows or is it the main blower that circulates air in the house?

Is this a propane or natural gas furnace?
Freon
Most Valued Contributor
 
Posts: 715
Joined: Sat Jun 18, 2011 11:26 am

- Coleman furnace won't ignite

Postby capablewoman » Tue Nov 05, 2013 3:23 pm

It's a propane furnace. I was considering having the propane company come out and check the pressure off the tank, as I rent the tank.

Regarding the blowers, the draft inducer kicks in at the call for heat as per the sequence, the HSI glows hot, the gas valve clicks, a blue flame starts from the first burner, but the rest of the burners fail to ignite, so the HSI turns off, waits then retries. After three tries, the main fan still turns on even if the burner doesn't fire and there isn't any heat.

I checked the vents attached to the chamber, and it's hard to say if they are clear. I suppose it is possible that something crawled in front the outside, where they are vented next to the house foundation. The vent tubes then run about 20 feet to the furnace after the elbow so hard to check those, but am going to try to run something in there to make sure there isn't a blockage.
capablewoman
New Contributor
 
Posts: 5
Joined: Wed Oct 30, 2013 3:20 pm

- Coleman furnace won't ignite

Postby Freon » Tue Nov 05, 2013 8:57 pm

When you have the door open, everything lights as you would expect. If that is correct then the burners are clean and working as they should.

Check how full the propane tank is... if it's low, get a fill and see if the problem goes away. Theoretically it should not matter.

Check the vent pipe for the furnace and make sure no debris is there. Possibly the inducer fan is doing just enough so the pressure safety doesn't trip but not enough draft (drawing oxygen into the combustion chamber) for the burners.

If the propane tank is old(er) have the company check the regulator pressure. However it seems adding oxygen (open door) makes things work so there's no lack of gas. The inducer fan is what draws in the oxygen so that's where I would focus your attention, including the vent piping.
Freon
Most Valued Contributor
 
Posts: 715
Joined: Sat Jun 18, 2011 11:26 am

- Coleman furnace won't ignite

Postby capablewoman » Wed Nov 06, 2013 11:31 am

The propane tank is at 60%. It was my thought too, that it sure seems like an oxygen issue, since the burners light with the door open. I watched the flame sequence with the door closed and noticed it lit the first and second burners yesterday, but then stopped, and shut down. So I turned it off and tried to feel for any build up/debris on the opposite end of the burner from the gas jets (which were clean), but I could barely get my small hand in there. So I carefully took a toothbrush and tried to clean up anything that might be blocking the flow of gas from burner pipe to burner pipe. That worked, as the next time I turned it on with the door on the chamber all burners fired normally. This morning at the call for heat, all worked great. Just now, when it kicked back in, no heat again.

I did check the vent pipe yesterday, all was clear from outside and the 20 feet to the bend in the pipe to the furnace itself. Inside the basement, all of the pipe joints were glued, so not easy to remove and check at that location. But from outside, I can feel the draw of air into the furnace at the pipe opening. So, Freon, you are probably correct in that I should focus on the inducer fan.

One more thought, could ANY of this have anything to do with the programable thermostat? Perhaps its faulty? I just changed the batteries in it, and turned off the program to run manually during all of this furnace issue, but it would seem odd to have that be the problem.
capablewoman
New Contributor
 
Posts: 5
Joined: Wed Oct 30, 2013 3:20 pm

- Coleman furnace won't ignite

Postby Freon » Wed Nov 06, 2013 3:43 pm

I doubt it's a thermostat issue since the fix so far is keeping the door off. The furnace is a 2002 so it's almost 12 years old. It would not surprise me the inducer isn't drawing the air into the combustion chamber like it used to.

As long as each burner flame seems identical to the others, then I would say the burners are not the problem.

You mentioned 20' of pipe. What diameter is the smoke pipe? Is the bend a 90 degree bend? It is possible the inducer is able to make the pressure switch close yet not able to drive enough air through the piping.

If the inducer assembly is easy to remove, you might try running 2 to 3 drops of 3-in-1 oil (blue can) down the inducer motor shaft. Also check that the small blower wheel is clean and there is no wobble in the shaft.

The theory of a draft pressure switch is when there's insufficient pressure for proper air flow to the combustion chamber, the system will not run. It seems your draft pressure switch is telling us there's the correct pressure which implies correct air flow. Since you're on the margins of operation (it runs sometimes) then it's possible the pressure switch should be shutting the system off but isn't due to age or design tolerance. Hopefully you can explore a little more before it starts getting too cold and you need dependable heat. I hate throwing parts at a problem... it can get expensive and be very frustrating.
Freon
Most Valued Contributor
 
Posts: 715
Joined: Sat Jun 18, 2011 11:26 am

- Coleman furnace won't ignite

Postby capablewoman » Thu Nov 07, 2013 2:02 pm

Since my last post, the furnace has been working on a regular basis, so think that the last thing I did handled the issue. I did look at the inducer yesterday and it seemed to be clean and running smoothly. Otherwise, temp has been holding steady for 24 hours now. Thank you for all of your help!
capablewoman
New Contributor
 
Posts: 5
Joined: Wed Oct 30, 2013 3:20 pm

- Coleman furnace won't ignite

Postby yogahelps2 » Wed Nov 13, 2013 11:28 am

So what was the last thing you did? From your posts it looks like it was replacing the thermostat batteries. What do you think actually fixed your problem?

We have a similar problem with our 20 yo Lennox Diplomat. Sometimes it just doesn't kick in when it's supposed to. Yesterday I tried to temporarily increase from 66 to 68 degrees, and I heard clicking and faint blowing (inducer fan) for 10 seconds, then it quit. (No flame at all that I could see with the cover on.) It repeated that about 5 times and then just stopped trying. Today I did the same temporary increase of 2 degrees and it worked just fine.

What should the HVAC mechanic do when he comes on Friday? I'd hate to pay $200 for him to come and say, "well, it looks fine now" without actually doing anything.
yogahelps2
Minimal
 
Posts: 1
Joined: Wed Nov 13, 2013 9:47 am

Next

Return to Residential

cron