Hi all. I have a Trane XL80 two stage forced hot air furnace, which is 9 years old. Last winter I found the furnace blower running, but the burners were off. Following directions that I read on one of the handyman forums, I cleaned the thermal control device (the little metal rod in the gas/flame path) with sandpaper. It worked and helped me go through the winter. Three weeks ago I started to sense the same problem however, this time cleaning the thermal control didn’t help. I tried to rub the rod with a dollar bill, a suggestion from an experienced technician but it didn’t help. Flipping the gas control switch on and off several times while the igniter was on (glowing) caused the gas flow and the furnace worked for a week or so but not anymore. Now none of the above “tricks” help. The furnace has two pressure sensors. Any suggestions how to track the problem? Thanks in advance for any ideas.

After spending $400 on parts and service with no luck. I moved the flame sensor from the far left burner to the burner second from the right. Had to drill one small hole and extend the flame sensor wire Now the furnace starts and runs on the first call for heat. I'm NOT a HAVC tech and my furnace is 10 yrs old and I use propane.

After spending $400 on parts and service with no luck. I moved the flame sensor from the far left burner to the burner second from the right. Had to drill one small hole and extend the flame sensor wire Now the furnace starts and runs on the first call for heat. I'm NOT a HAVC tech and my furnace is 10 yrs old and I use propane.This is DANGEROUS! The original location of the flame sensor is important to proving that ignition was successful on ALL burners. If raw gas is overfed, look out. :eek:

Moving that can cause this.