High-limit thermostats are safety devices that prevent electric clothes dryers from overheating by cutting off power to the heating element. During normal operation, the dryer's primary thermostat maintains a safe temperature inside the drum, but if it fails the high-limit thermostat cuts power to prevent overheating.
A high-limit thermostat sits between a dryer's power source and its heating element. Usually, the current flows freely to the element and is regulated by the dryer's main thermostat. If the main thermostat malfunctions, the high-limit sensors detect the rising temperature inside the dryer and interrupt the electrical circuit, shutting off power to the heating element. This often happens because of clogged duct work or problems with the blower.