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Discussion Starter #1
I have a Trane gas furnace - about 22 years old or so - with a honeywell S8910u universal hot suface ingition module installed about 4 years ago (by a professional, not me). Not sure if this matters, but I see it has a yellow (B) tab that says 3 tries. The HSI is a new Honeywell universal glowfly installed about 3 months ago.

Ok, here is the problem. This afternoon, I happened to be near the furnace when I heard the call for heat ( and I know the usual sequence very well) - I seen the igniter glow orange for about 30 seconds - then seen it just shut off as the gas would not click and turn on. I did not hear the gas try to click on at all - I then waited (after a min or so)for the next try - and again the igniter will glow red/orange like usual - for 30 sec - stays bright- and then no gas clicks on -as the glow fades from igniter as it shuts off.

This went on for 4 tries , which I thought would only have 3 tries fail before lockout - I was surprised to see it keep trying beyond that. Also - while it was going thru this sequence- the green light on the ignition module is green with a pulse, which says is normal operation.

This is what I did and have no idea if this was just a coincidence - I "reset" the draft sensor button (natural draft, no motorized) and then the next sequence -I think the 4 or 5th try - the gas ignited as it normaly does and the furnace worked as normal.

After the heat call was done - I shut off power to the furnace for about 5 min -and then turned it back on. I went to call for more heat - and the normal sequence of igniter glow - click for gas - ignite - heat - blower- turn off all worked fine as I tried 2 more times.

My question is - if this turns out not to be a real fix and happens again (like if the furnace is real cold for hours and tries to start) - what should I check for - I have a multimeter - I just want to get ahead of this and be prepared to do something as I dont want to wait for it to fail and never turn on during a cold snap.

Any help on what could cause this issue I described -is greatly appreciated
 

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Check if the gas valve is getting 24 volts while the hot surface ignitor is glowing. If it is then you check if there's gas flowing.
 

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If you reset the spill switch. Check the chimney for problems.
 

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Discussion Starter #4 (Edited)
Thanks for the help. I did check the voltage at the gas valve- I am not sure I did it right however- I followed the wire that from the "valve" line on the ignition module to the valve, and the "valve ground" line to the valve. When the igniter started to glow - I had the multimeter set to volts on both points on valve -and the volts I think was something like 6 or .06 -then once the time came for gas ( after 30 secs of igniter warm up) the meter flashed "OL" quickly -gas came out and ignited like usual and immeditiatly the meter said and maintained 27 volts.

So - there was not voltage at the valve prior to the call for gas , then there was voltage after gas was flowing and burning.

As for as the spill switch, all I did was press the button in, it did not feel like it tripped, there was no resistance to pushing it in or any click. I think it was coincidence about that.

So far, the furnace has been working the way it should since I turned it off and on yesterday , igniting on the 1st try and runs as normal - My question though is this - since it happened at all - the fact that it was not confidently going from igniter to gas even one time- does that mean that the ignition module - although only 4-5 years old - is going bad?

Is there a way I can further check the module with the meter to see any weak areas - if someone can help me with what to look for based on the description of the symptoms it had yesterday would be greatly appreciated -
 

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gas flow

Undo your gas line at the gas valve and see if you have debris at the inlet strainer. If not check if you have a gas regulator that is malfunctioning or freezing.
 

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Post a pic of the reset you are resetting.
 
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