# Gas supply shuts off early



## amyjamie (Oct 15, 2010)

I have a Trane XL 80 furnace that was cleaned last week.  On turn on today, the gas supply shuts off about 4 seconds after ignition.  I bypassd the thremal limit swtich and get the same result.  Any suggestionms?


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## kok328 (Oct 15, 2010)

Make sure the flame sensor is in the pilot light to recieve a signal that the pilot light is on.


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## paul52446m (Oct 15, 2010)

amyjamie said:


> I have a Trane XL 80 furnace that was cleaned last week.  On turn on today, the gas supply shuts off about 4 seconds after ignition.  I bypassd the thremal limit swtich and get the same result.  Any suggestionms?[/QU
> 
> The flame rod in your pilot was not cleaned. these flame rods get a film build
> up on them that you can't see. Take some emery cloth or fine sand paper
> ...


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## mjocius (Dec 18, 2012)

I am having a similar issue.  My Xenon furnace is 10 years old.  We had someone come out and clean/tune it up this year and he 'discovered' that our two stage furnace was running in one stage, so he supposedly set it back to two stage.  Since then, our furnace is having startup issues.  Blower will start.  I will then hear the flames kick in, but it doesn't sound very strong.  After about 10 seconds, the flames go out.  Blower will continue to blow and the cycle repeats until it eventually starts correctly or shuts down completely.  Second repairman and company have replaced circuit board, pressure switch and thermostat.  Still same problem.  Any ideas?  Guy coming back out to the house on Friday and I'm NOT paying for anymore repairs!  Furnace is still set to run in two stages.


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## tinmantu (Dec 18, 2012)

Depending on the year of the trane xl, the older models had two screw holes on the flame sensor.  I remember one of my first times servicing one that I got it in the wrong hole and it was a good lesson....not saying that's your problem, but the flame should be covering it completely, not partially.


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## joechuckg (Dec 21, 2012)

Make sure flame sensor is also clean/polished with some sand paper until shiny chrome


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