i have a train xl80 furnace. When it calls for heat the draft inducer fan turns on and then the burner fires up for a short time then shuts off then it starts all over again.I am thinking its the flame sensor. please help.
Train xl 80 unit fires up then shuts right off
furnace
Best Answer
I just yesterday dealt with one like that. It had electric ignition (glowing ignitor) and a single yelloow "flame sense" wire. This is only the second one of these I've found in a decade, but the problem and the solution is the same. IF your unit uses ion flame detection, the burner ground has become oxidized. It may look like metal against metal, but a fine coat of invisible oxidation had formed between the metal parts. It needs a good "ground reference" before it can detect the ions.
To fix this, I removed the burner. While I had it out, I scraped the flame rod tip some but it wasn't really dirty. When I put it back in, I intentionally made one of the self-tapping sheet metal screws dig a new groove instead of putting it back in the first grooves. I also got it good and tight.
Just as in the first case, the mere act of disturbing the mechanical assembly caused a better ground to be formed. It must be working, because I didn't have to get up last night and go fix it.