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Coleman DGAA090BDTA furnace flame quits after 20 minutes, below thermostat temperature. Fails after 3 auto attempts to reignite. I power cycle unit, still does not ignite. Wait 15 minutes, reignites on first try, burns for 10 minutes, quits. Wait 10-15 minutes, again works fine for 5 to 10 minutes. Repeat. Not really short cycling.

Doesn't matter if filters are on or not, and filters are clean anyway. Cleaned flame sensor. Made no difference. All duct vents are open. Doesn't seem to be limit switches because when I unplug limit switches, fan kicks on. I've read as many DIY sites as possible, several similar questions on this site...watched videos... nothing quite like this.

  • If it was a high limit it should require a Manuel reset (or the furnaces I have installed have this so something has to be pushed to reset) is it possible a power cycle is clearing a high limit alarm? Especially since it takes time to reset. – Ed Beal Jan 24 '18 at 20:18
  • Thanks Ed. Tested the limit switches. Both have zero ohms. Upper reset button is not tripped. Control board is discolored (brown, like it has experienced some heat) around three resistors. Oddly, after a couple of failures this morning, it is working fine now for the first time in several days. – Pancho Jan 26 '18 at 16:38
  • "when I unplug limit switches, fan kicks on." - which fan, the inducer or the blower? I've never worked on a Coleman, but on Yorks, the inducer fan running all on its own is the 'error code' for limit switches. To really test the high LS, you'd need to see how hot it can get before it trips... or just buy a new one and be sure it's not that. – Mazura Jul 25 at 17:13
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It sounds like a component is failing. Could be the circuit board or the gas valve. When you say it tries to light does it glow and fail to ignite? Does it ignite briefly and then go out? Most likely a component is getting hot and loosing connection. Could be the vent proving switch if there is no glow. The combustion air is being taken from the roof since it is a sealed combustion furnace. The return air is coming from inside the house. The vent motor should come on. Several seconds later the igniter should glow red. After a few seconds the gas valve should open. 45 seconds or so later the blower should come on. By using a volt meter at each component check if there is 24 volts present at each component at the proper time. If there is voltage at the gas valve for instance and the valve does not open it is the gas valve. I once worked on a furnace for 2 years before it would fail for me. The owner said it would not operate when cold but by the time I got there it was working fine. Finally it wasn’t working when I got there. I was getting voltage to the gas valve but no gas. There was a bad solder joint inside the valve that would make enough contact once it warmed up a bit.

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It is possible that it is not getting enough combustion air. I found this once on a Coleman. Make sure snow is not blocking air-intake. And sometimes the intake aperture gets reduces because of snow load. Some of these furnaces will shut down when not getting enough combustion air.

  • Thanks Paul. Air intake is the house itself through the furnace closet door. Unfortunately we haven't had enough snow this winter to even shovel the deck. – Pancho Jan 26 '18 at 16:40

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