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Old 01-01-2009, 10:36 AM   #1
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Furnace fails to ignite now and then...


Hi... I have a 7 year old Trane XL 80 gas furnace. A week ago I was near the furnace (in the garage) when I heard it do its normal "calling for heat" cycle with the draft fan starting up, I saw the hot surface igniter begin to glow, heard the solenoid of the gas valve click but then nothing, no ignition of the gas... As I subsequently learned it is supposed to do in such failure events, it cycled itself down and then a minute later or so, tried again... On the second attempt it worked and the gas ignited...

There are no failure codes showing up on the flashing red light, instead just the normal calling for heat fast flashing or the calling for no heat slow flashing when the furnace is in one or the other of those modes, in other words nothing to learn from any error codes...

It fails to ignite the gas maybe one time in every 10 attempts and so far it has always worked on the second try if it failed on the first...

My furnace guy came out and bascially suggested doing nothing until it "really broke" but I wasn't too happy with that idea.. He asked me if I was able to hear the hiss of gas during these failures and I told him I couldn't say for sure because the fan noise tends to mask that... But since the igniter seemed to be working I took a chance and told him to go ahead and replace the gas valve ($200) which he did... But the next day, it failed yet again... I carefully listened until it failed again and on this next failure I am confident I heard gas flowing... So that told me it must be a weak igniter maybe??? Anyway, I bought the recommended igniter ($60) and replaced it myself... It worked all the rest of that day (yesterday) but today I saw it fail yet again...

So now to my question... What else can it be?? The control board??? Other things?? Assuming I really do hear gas flowing and the igniter is glowing orange, what could be going wrong that causes it to not ignite now and then???

Any help would be much appreciated... thanks.. bob...

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Old 01-01-2009, 12:00 PM   #2
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Have him remove and blow out the burners with compressed air and then rinse them with hot water in the sink. Check the face of them for deposits of ash etc.

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Old 11-22-2016, 07:06 PM   #3
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Re: Furnace fails to ignite now and then...


Hi I have a tempstar gas furnace that goes into soft lockout on max trials reached. Then after power reset it ignites on the second trial. I had the gas valve , flame sensor, air filters replaced. Looking at diagnostic led flashes continuously. What could be wrong now
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Old 11-22-2016, 07:57 PM   #4
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Re: Furnace fails to ignite now and then...


Gas pressure? Cleaned burner assembly? Hot surface igniter resistance and voltage?
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Old 11-22-2016, 11:12 PM   #5
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Re: Furnace fails to ignite now and then...


Quote:
Originally Posted by Mack1375 View Post
Hi I have a tempstar gas furnace that goes into soft lockout on max trials reached. Then after power reset it ignites on the second trial. I had the gas valve , flame sensor, air filters replaced. Looking at diagnostic led flashes continuously. What could be wrong now
What's the amp draw on the HSI? Was it replaced recently? (i usually don't replace gas valves unless the pressures clearly show a problem, since it's rare for them to fail intermittently)

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Old 11-23-2016, 04:56 PM   #6
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Re: Trane XL80 Furnace fails to ignite now and then...


Replaced igniter and cleaned the heat sensor with steel wool in Trane XL80 furnace. Worked great for 2 weeks and then had the same problem and cleaned the heat sensor with sand paper in greater detail which lasted 1 week and now I am getting the 2 red blinking lights. The fan does blow cold air off and on and I am presently getting heat for two hours after resetting the system. Do I need to change my thermostat? "Honeywell Energy Star Chronotherm IV Plus" Any suggestion or next steps appreciated.
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Old 11-23-2016, 04:57 PM   #7
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Re: Furnace fails to ignite now and then...


The furnace and thermostat are original at 15 years old and appear to be in great shape.
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Old 11-23-2016, 05:19 PM   #8
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Re: Furnace fails to ignite now and then...


You need to use your meter and instrumentation to take readings and measurements to diagnose what's wrong. First thing is to take an ma reading on the flame sensor with your meter.
Your chances of fixing the problem by blindly throwing parts at it are very low.
Thermostats are often blamed but are rarely the cause of problems.

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