Trane XE80 Runs for 4 seconds and stops.

[R22helopilot]

I have a Trane XE80 that calls for heat. It starts and runs for about 4 seconds and stops. It does this 4-5 times and when it stops it show no call for heat.   I have replaced the over heat sensor, and controller and gas valve have been replaced in the last 2 years.

Please Help..........

[dracula1227]

When you say over heat sensor I am assuming you mean the flame sensor if that was was replaced 2 years ago it may just be dirty you can use a Scotch bite pad to or steel wool to clean the rod I don't recommend sand paper or Emory cloth if you know how to take a microamp reading I would do this before you clean it and then after to compair if you get a lager number after you clean it and it stays running its a good bet your done if no change check the wire to the board or its possible a bad board but sounds like just a dirty flame rod hope this helps

[JWWebster]

[romanowski72]

I think dracula is correct you also might might be able to bypass the heat sensor but I have never tried it before cleaning the sensor has always fixed the problem.  Also it would be out of sequence on most furnaces but maybe check for draft inducer blockage or pressure switch.  If no draft is detected the furnace will also shutdown.

[JWWebster]

Glad to have ye on board Romanator