The high limit thermostat is a safety device mounted on the heating chamber and is designed to prevent the dryer from overheating when the exhaust vent is restricted. A restricted vent will cause the high limit thermostat to trip or activate, interrupting the circuit to the heating element or gas valve. The high limit thermostat is not designed to activate repeatedly like a cycling thermostat and will eventually fail causing a no heat symptom. Disconnect the power to the dryer and check the thermostat for continuity with a multi-meter. If there is no continuity then it will need to be replaced and the restricted vent system corrected as well.
