How To Check A Dryer Thermostat

If you suspect that you have a defective dryer thermostat, you should first check for a dryer vent restriction. Since dryer control thermostats are in the air flow that exits the dryer, a dryer thermostat cannot cycle the dryer heater if there is no air moving past it. If you have a vent restriction then your dryer will be getting too hot. You may notice that the dryer is hot on top, very little lint in the lint filter, and that the clothes take an unusually long time to dry. This is the reason most people want to check a dryer thermostat.

If you are positive that you do not have a dryer vent restriction, and want to check your dryer control thermostat, you will first need to disconnect the dryer from the electrical supply and gain access to the thermostat.

Thermostats are located in different locations on different brand dryers. However, a control thermostat will always be in the air flow. In other words, the side of the thermostat that senses temperature will be exposed to the dryer airflow. Do not confuse control thermostats with high limit thermostats or dryer safety thermostats. These kinds of thermostats sense the direct heat from the heater.

Okay, now that you have gained access to your dryer control thermostat, checking a thermostat is simple because it has one electrical path in and out.

Use an ohmmeter and check for continuity, there should be no resistance. Technicians check to see if a dryer thermostat is cycling by using a voltmeter. When a dryer is operating and the thermostat cycles the voltage across the thermostat is 220 Volts. A non-technician should never check a dryer thermostat while the dryer is plugged in. An inexperienced person should always make sure that the dryer is disconnected from the electrical supply and use an ohmmeter to check for continuity.

It is not necessary to remove the thermostat from the dryer to check it. However it is very important that you remove at least one of the wires from the thermostat so that the only electrical path you will be reading is in one side of the thermostat and out of the other. Since you will be checking the thermostat at room temperature, the electrical contacts inside the thermostat will be closed. In other words, the circuit will be complete in one side and out the other. The resistance reading on your ohmmeter will be zero indicating that the electrical path through the thermostat is complete. If the electrical path is complete through a dryer thermostat, and the dryer is not heating, the problem is not the dryer thermostat.