I have a Trane XL80 furnace. Basically, when it receives a call for heat, it ignites but cannot maintain the flame. As soon as the flame ignites (or within 10 seconds), it cuts off the gas flow and starts the ignition process again. It does this until the furnace locks out. Sometimes (probably 10% of the time) it maintains the ignition.

Here is what is really strange. Three times I have had a service person look at it. They have replaced NOTHING and yet it seems to work when they get here and after they leave. Then a month or two later the same problem starts again. The service people even tell me, "I don't see any problems."

Please help! I'm beginning to think my furnace is possessed.

Next time the person is out for service have them clean the flame rod/sensor if the unit has one.

Thanks for the response, but I've already cleaned the heat sensor. There is something else wrong.

I am sure there is something else wrong but the problem is intermittent and thus hard to find. You will probably need to back track from the gas valva back to see what is the part that is causing the failure. This can be very time consuming. The next option is to start replacing parts but that is just far to expensive. See if there is a proving switch on the combustion blower assembly. That has also been shown to cause an intermittent problem.

I had what sounds to be the same problem. I cleaned the flame sensor which is a small rod that extends out into where the flame shoots out. 1 screw and it comes out and there is a wire attached to it. Just take it out and sand it down some and reinstall. Hope this helps someone because I was a little worried about getting a big repair bill.