Trane XE90 Won't stay lit
 

I have a Trane XE90 with a problem. The LED flashes like normal when it gets a call for heat, the glow plug warms up, the gas relay opens, gas flows to the burners, the burners light for a couple seconds then turn off. I've replaced the flame sensor and installed a refurbished control board thus far - still same problem. Any ideas? Thanks!

Welcome Nifaron:
Make sure the vent pipe is clear and clean the heat exchanger tubes. The furnace shuts down if there is a back-pressure on the vent. If it has already worked for several years, it has to be something that changed to affect it. Maybe a bird's nest in the end of the vent?
Glenn

Would I be able to test that by disconnecting the vacuum hose? In my earlier testing I disconnected it with the same result. In any case, I'll go to the basement and start looking at the vent.

Thanks much!
Aaron