A flame dirty flame sensor can cause a furnace to light and go back off on a call for heat because the flame wasn't detected. Then it retrys until lock out. Not what the op described as happening. He said it randomly turns on for a minute and shuts off and other wise heats normally.
I meant that earlier post as good natured ribbing because I believe you are on the wrong track and made your comment about people not knowing what they are talking about. you seem like good guy and always try to help people here and that makes you ok in my book
