Hi Erik, It sounds like a bad combination fan/limit control. Have the repair man check the heat exchanger for cracks and also check for carbon monoxide. Im sure the repairman will check the sequence of operation several times and note any problems. Please let us know what he finds. Good luck!
“Now the freaks are on television, the freaks are in the movies. And it’s no longer the sideshow, it’s the whole show. The colorful circus and the clowns and the elephants, for all intents and purposes, are gone, and we’re dealing only with the freaks.” - Jonathan Winters