The purpose of the thermal fuse is to prevent fires by detecting when the dryer drum is overheating and tripping in response. The dryer will therefore stop running. A thermal fuse is a one-time-use component, but luckily, they are inexpensive and easy to replace. The main reason that a thermal fuse will blow is a blocked exhaust vent. When the exhaust vent is blocked, hot air cannot properly get distributed out of the dryer, which causes it to overheat.