The part(s) or condition(s) listed below for the symptom Dryer won't stop are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
If the vent is clogged or partially clogged, it will restrict the airflow through the dryer, substantially increasing the drying time. To ensure proper dryer performance, you should clean your dryer’s venting system at least once per year.
Gas dryers have two or more gas valve solenoid coils. The gas valve solenoids open the gas valve ports to allow gas to flow into the burner assembly. If a solenoid fails, the burner may run intermittently. If the burner keeps shutting off, the dryer won’t heat properly and may not stop. To determine if one or more of the gas valve solenoids has failed, check the igniter. If the igniter glows and goes out but does not ignite the gas, the gas valve solenoid is defective. If one or more of the gas valve coils are defective, we recommend that you replace them as a set.
The cycling thermostat cycles the heat on and off to regulate the air temperature. If the cycling thermostat is defective, the dryer will not heat. However, this is rarely the case. Before replacing the cycling thermostat check all the more commonly defective parts. If you have determined that all of the other components are working properly, test the thermostat by using a multimeter to test for continuity. If the thermostat does not have continuity, replace it.
If the dryer won’t stop, the thermistor might be defective. Some dryers have a thermistor. The control board uses the thermistor to monitor the dryer temperature and cycle the heat on and off. If the thermistor is defective, it may turn off the heat too early, considerably lengthening the drying time. However, this is rarely the case.
Dryer thermistor. This thermistor should read approximately 50,000 (50K) Ohms of resistance at 77 degrees Fahrenheit. *Note that it is not in the heating circuit so it likely will not be the cause of a dryer heating problem. It can however effect cycle times or cause a fault if defective.