How Dryer Heating Elements Work

When a dryer is not heating, the first thing everyone suspects is that the heater is defective. While it is true that dryer heaters fail a high percentage of the time, it is not the only thing that will make a dryer not heat. However for the purpose of this section, we will assume that you have a dryer that does have a defective electric heater.

A dryer heater is made up of a resistance wire, held in place by ceramic insulators. Ceramic is used because it is an excellent insulator, and is able to operate under the extreme conditions of holding a red hot resistance wire in place. The resistance wire inside a dryer heater is used to slow down the electrons and create friction. This friction is what causes the resistance wire inside the heater canister to get red hot. In fact, it is amazing that dryer heaters do not fail more often.

Once you have isolated the heater by removing the wires attached to the terminals that lead into the resistance wire, you can use an ohmmeter to check for resistance. All dryer heaters must have resistance to the flow of electrons to work properly. Resistance is measured in ohms and an ohmmeter is used to measure resistance. The meter sends out a small amount of electrons, and measures the amount of electrons that went out, compared to the amount of electrons that came back. This calculation is displayed in the meter digital display as a measurement of ohms. The resistance of a typical dryer heater is about 5 to 20 ohms. When you check the dryer heater, if your meter continues to blink, that is an indication of an open circuit. In other words, the path in and out through the resistance wire is broken. Before you condemn the dryer heater, you need to take your meter leads and touch them together. Watch the display on your digital meter as it should drop down to zero, indicating zero resistance in your meter leads. This will confirm that you had the meter set properly to read ohms and that the heater is in fact defective.

If you find that you have an open dryer heater, it is not necessary to check any other components within the dryer. The only exception to that is the possibility that the dryer control thermostat was stuck, and the high limit thermostat was cycling the heater on and off. This could be because of a defective control thermostat, or it could be because of a vent restriction. Because of the risk of fire, anytime you service a dryer you should confirm that the dryer vent is not restricted. Typically this is done by turning the dryer on and going outside to the vent to check the airflow.