Just noticed with the furnace... it has been running for at least 15 minutes, putting out heat. I walk out into the garage and it doesn't sound right. I looked at it, and it was in the middle of relighting the burners, when it should have been running continuously for another 15 minutes or so. OK... so that's a problem. I put a new main control board on it in January of 2014, after the previous baord started failing (blinking LED light indicated "replace board"). The furnace is nearly 20 years old, a Trane 92% efficient unit. Flame sensor dirty / flaking out? Thermostat flaking out? (Dropped a call for heat, and then started calling for heat again?) Control board flaking out (again)? If it was a flaky/failing flame sensor, would have it re-fired without shutting completely down first? No code was being flashed by the LED on the control board.