How To Test An Electric Dryer Thermostat

If clothes are still wet after you take them out of the dryer, test the thermostat. Dryers commonly have two thermostats: a high limit and cycling thermostat.

The cycling thermostat is responsible for shutting off the heating element after it reaches a preset temperature. The high limit thermostat serves as a safety feature. Here are tips to test an electric dryer thermostat.

Prepare to Work

For this project, you need:

• multimeter
• one-fourth inch nut driver
• needle-nose pliers
• small and medium flat-blade screwdriver 
• Phillips screwdriver
• hot plate or electric griddle

Unplug the power cord to the dryer. For extra safety, shut off the breaker that controls power to the room. Pull the dryer a short distance from the wall.

Remove the Thermostats

Use a Phillips screwdriver or nut driver to remove the back panel screws. Locate the thermostats.

The cycling thermostat should be on the lower left side in the blower wheel housing or inside the vent system. The high limit thermostat is located on the heating element conductors. The thermostats commonly are no longer than two inches with purple and orange wires attached.

Make a note of how wires attach to the cycling thermostat, or take a picture. Examine the wires for damage, and replace the thermostat if it has damaged wires. Otherwise, proceed with the test.

Remove the wires from the terminal connector using the needle-nose pliers. Detach the screws with a nut driver. Remove the thermostat, and lay it on a flat surface.

To remove the high limit thermostat, use a small flat-blade screwdriver to lever the wire connector. Remove the housing from the mounting tube with the large flat-blade screwdriver. Lean the thermostat forward, and detach it from the slot.

Test the Thermostat

Let the thermostats get to room temperature for a more accurate reading. Set an analog meter on the lowest resistance or 0. A digital multimeter should set itself to 0.

Touch the contacts to the silver terminals on the cycling thermostat..If the reading is still 0, then the thermostat is operating properly. Any other reading indicates a failed thermostat.

Check the high limit temperature that should be printed on the mounting flange. This number will say "L130" or "L120"; meaning it is the highest temperature limit.

Place the cycling thermostat on the griddle or hotplate, and set it to the high limit temperature. Wait several minutes, then touch the contacts to the gold terminals. 

You should get a reading between 1000 and 1200. If the thermostat turns the heating element off, or it displays a 0 reading within 5% of the high limit temperature, it means the unit is operating properly.

Touch the test probes to the terminals in the same manner as the cycling thermostat. This doesn't require the griddle test.

Reinstall the thermostats, and restore power. If you still can't find the problem, contact an appliance repair service.