I have fan problem with my Trane furnace. When I set the temperature to 72, and turn it on to heat up the house, it works for about 5 min (reading temperature is 65) and then the fan shut off, but the fire stays on.
I put the heat/cool to "off" and the fan to "on" (not auto), just turn on the fan. The fan turns on but shut off after 20 to 30 sec. About 30sec later, it turns on again. But it shut off again in about 20 sec. Then it cycles likes this way.