No heat! Trane XE80.

[smokehouse]

hello! I have a furnace (Trane XE80) that recieves the call for heat, ignites the burners but they stay lit for only a few seconds. It will try 3 or four times to do this. They stay lit for a few seconds, then go out suddenly. After that, the fan kicks on and the unit blows cold air. Thanks for your time!

Edited November 14, 2012 by smokehouse

[jumptrout]

Are all burners igniting or just the first burner at the igniter?

Any codes flashing on the board after failure?

[smokehouse]

All burners are igniting; can't see any error codes- just the call for heat code.

[jumptrout]

Your flame sensor should be cleaned carefully with steel wool.

That may correct the problem and keeps the burners on.

[smokehouse]

New development! After shutting it down for an hour or so, now it seems to be working; but it did the same thing yesterday, so I'm not trusting this thing!

[smokehouse]

Thanks for your time Jumptrout! What does this part resemble? I see a small resistor-like part coming out of a ceramic mounting base about 6" away from the burners (says "microtherm" on it). My meter show continuity through this part at all times, regardless of the burners being on or not. Does this sound like the part to which you refer? OR, would it be the part that seems to be mounted on the sheet metal above the burners (has "Texas Instruments" on it, if that helps) that's wired in series with the other part I mentioned earlier (as well as a diaphragm switch), and is a rectangular shape about 1.5'X2.5"? Thanks again for your time!

[smokehouse]

Now getting error code- "system lockout, no flame, check polarity" after several failed attempts to keep burners lit!

[jumptrout]

Reset all your rollout switches.

[Bullstok]

flame sensor, as said, probably needs cleaned. most of the time it is a single steel rod that sticks into the flame. usually in front the last burner, opposite the ignitor (the part that glows red when lighting). it is likely held in by a 1/4" hex head screw and the sensor has ONE wire hooked to it that goes to the control board directly. (i dont know ur particular furnace specifics off hand.) when the sensor gets too dirty (soots up) it sometimes works and sometimes doesn't.

Edited November 15, 2012 by Bullstok

[smokehouse]

Thanks for the replies, gentleman! How does one go about resetting the rollout switches, Jumptrout?

[smokehouse]

Found that part and cleaned it, Bullstok- although it seemed clean. So far all seems well! Thanks for your help, Jumptrout and Bullstok! Will keep an eye on it! Will donate to the beer fund!

[jb8103]

Thanks for the replies, gentleman! How does one go about resetting the rollout switches, Jumptrout?

Jumptrout will be back to advise on the switches, meanwhile, maybe try to find a new flame sensor. Shouldn't be more than $20.

[jumptrout]

The rollout switches look like this. Probably 3 resettable switches.

http://www.qcsupply.com/20875-modine-flame-roll-out-switch.html?utm_source=shopzilla&utm_medium=cpc&utm_campaign=productfeeds

[Bullstok]

although it seemed clean.

yep, a lot of times they look pretty clean. but the buildup can be like a thin film. it insulates the rod from the flame. the rod is not trying to be heated by the flame (as a thermocouple does) it is conducting electricity through the path of the flame (not exactly, but close enough). if you picture that it is operating this way it is easier to understand that it has to be good clean steel so it can conduct electricity. a good scrub once a year with a scotch brite pad will usually fix it up. if the rod is black and sooty it may indicate poor combustion and the problem would need looked into.

these sensors hardly ever need replaced. if the ceramic insulator is busted or the wire connection area is bad then yes, replace it. but if there is still steel forming the part in the flame, that can be cleaned, then it should be fine.

Edited November 16, 2012 by Bullstok

[Daveb1972]

these sensors hardly ever need replaced. if the ceramic insulator is busted or the wire connection area is bad then yes, replace it. but if there is still steel forming the part in the flame, that can be cleaned, then it should be fine.

I concur, the sensors very rarely need to be changed. Physical damage is what often takes them out.

[smokehouse]

Thanks for the help, gentlemen! That furnace is working just fine, and I've learned something new. Have a great Thanksgiving!