How to Test a Defective Gas Dryer Flame Sensor

Remove the screws that secure the access panel at the bottom front of the dryer. Use a Phillips screwdriver or nut driver, depending on the model. Turn the screws counterclockwise, remove them and remove the panel.

Locate the thermocouple, which connects to the pilot light at one end and the gas valve at the other. The thermocouple is generally a round device that looks like a pencil with a long wire attached to it. It is located between the pilot light and the valve on the gas line. There is no need to shut off the gas supply since the valve only allows gas through when the thermocouple is operational.

Remove the end of the thermocouple from the gas valve using an adjustable wrench. Fit the adjustable wrench around the fitting on the end and turn it counterclockwise.

Set your multimeter to DC milivolts. A multimeter, used to test electrical current, can be purchased from a home improvement store. It has differecnt settings for testing various electrical conditions, the DC milivolt setting is use for testing thermocouples. Consult the multimeter manufacturer's instructions as needed.

Place one of the multimeter probes on the side of the thermocouple and the other probe at the tip of the end that was attached to the gas valve. If the multimeter reads less than 15 milivolts, the thermocouple is ineffective and should be replaced. A new thermocouple should read about 32 milivolts and will lose voltage with wear.