A thermal fuse is a small device – just an inch or two long – that plays a critical role in preventing fires. Federal law mandates the inclusion of a thermal fuse on all dryers manufactured since the 1980s. A thermal fuse operates if dryer exhaust temperatures climb too high. The fuse shuts off the dryer or its components if this happens. A thermal fuse only works one time. If it triggers during a high-exhaust temperature event, the fuse must be replaced.
Many dryers simply will not run once a thermal fuse triggers. On other models, the drum continues to turn and the dryer operates, but the heating element does not. Clothes come out of the dryer wet once the appliance completes its drying cycle. Manufacturers are not consistent from model to model, even within the same brand.
Locate the Fuse
Thermal fuses are installed on the dryer’s exhaust duct. Typically, you must remove the back panel of a dryer to access the fuse. Ensure to shut off electrical power to the dryer before attempting to locate and troubleshoot the fuse. Most dryers plug into a 220-volt wall outlet, so you can unplug the unit to cut off power. Thermal fuse shapes and sizes vary. Some are made from plastic; others are metal. Look for a small device about the size of a quarter to about 2 inches long, mounted directly on top of the exhaust duct. A thermal fuse has two wires connected to it.
A reliable method for testing whether a thermal fuse has burned out is to temporarily bypass the device. However, it is tempting to operate the dryer this way, or forget to replace the fuse once the dryer is running. Bypassing the fuse is only a quick means of detecting whether the fuse is bad. It is not a permanent fix. Disconnect the two wires from the fuse and tie them together with a jumper wire, then turn on the dryer. If it runs and heats, the thermal fuse burned out and must be replaced.
A better, faster means of testing requires an electrical multitester set at its lowest RX setting. Remove the two wire leads from the thermal fuse and touch a multitester probe to each wire terminal on the fuse. If you get a reading of infinity, the fuse is fine. Any reading less than infinity indicates a triggered thermal fuse you will need to replace.
Replace the fuse with an exact match for your dryer make and model. Then check the dryer for a reason why the fuse burned out. Sometimes, age wears out a fuse, but other times something else failed and caused exhaust temperatures to rise. Ensure the power is still off before troubleshooting, then examine the exhaust duct for obstructions that limited air flow. Check the blower motor fan blades for breakage, and ensure the motor isn’t binding. You may also want to replace the dryer cycling thermostat along with the thermal fuse. If this thermostat fails, it will likely trigger the thermal fuse.