How Dryer Thermal Fuses Work

A dryer thermal fuse is connected in series with the dryer motor electrical circuit. If there is a condition that causes excessive heat such as a vent restriction or a defective control thermostat / thermistor the thermal fuse will open and interrupt the motor circuit causing the dryer to shut down.

A thermal fuse is a one time fuse and must be replaced before the motor will start up again. If this fuse is bad the motor will NOT hum. If you find the thermal fuse open you must address the condition that causes the excessive heat. Another name for the thermal fuse is a safety fuse or safety thermostat.

Dryer Safety Thermostats
Dryer safety thermostats, thermal cutouts and high limit thermostats only come into operation when there is an unusual condition in your dryer that causes too much heat. Under normal dryer operating conditions these items do not function. Vent restrictions are the number one reason dryer safety thermostats, thermal cutouts and high limit thermostats stop the heater from heating or open the circuit to the motor causing the dryer to shut down.

Dryer safety thermostats and dryer thermal cutouts and high limit thermostats are located in close proximity to the heater. When temperatures outside the normal operating range are sensed the dryer safety thermostat, thermal cutout or high limit thermostat interrupts the circuit to the heater or the motor.

Since dryer thermal fuses and dryer safety thermostats are simply switches that are normally close and only interrupt the circuit to the heater or dryer motor, appliance service technicians use a jumper wire to temporarily eliminate the fuse link or thermostat from the circuit. Once the jumper wire is applied from one side to the other of the thermostat, the technician will attempt to duplicate the complaint to see if the dryer will start or if the heater will come on. DO NOT EVER LEAVE A JUMPER WIRE IN THE CIRCUIT! Since the dryer thermal fuse and dryer safety thermostat is a safety device, leaving it in the circuit could CAUSE A DRYER FIRE. After you make your diagnosis and determine if the thermal fuse is defective, it must be replaced before the dryer can be operated.