Scamp furnace..

[Spencer]

My 13' Scamp has a furnace, while staying in it last night (<30°F) the furnace had no trouble starting. The problem starts when it shuts down. The flame is suppose to die, then when the unit cools down some, the fan is supposed to quit. Mine all wants to stop at once, sometimes the fan is the first to shut down, before the flame, and before it cools back down. On a few occasions it did what it was supposed to do, but not always.
Any ideas what the problem is?

[steve dunham]

Defective or dirty fan limit switch . The fan limit has 2 switches ,one switch shuts off the gas valve when the hi temperature limit is exceeded (safety) and a second switch that starts the fan when the air temp has reached a certain temperature and keeps the fan running to extract all the heat from the furnace at the end of a heating cycle