Most clothes dryers have a thermal limiter or fuse, which is a heat-sensitive safety mechanism that shuts off heat to the drum or the power supply to the dryer if it overheats. Unfortunately, you can't replace a thermal limiter once it activates. The only choice you have is to replace it; your dryer won't operate properly until you do.
A thermal limiter only initiates when the air temperature in the drum reaches a predetermined trip temperature, usually the point overheating starts. A dryer can overheat for a number of reasons: restricted airflow, blower motor freezes, faulty thermostat or the heating element malfunctions. After it activates, the thermal limiter immediately cuts power to the dryer to avert a fire from ensuing.
Reset Vs. Replace
Although you can't reset a thermal limiter that has been blown, you can reset the dryer's two circuit breakers and restore heat to the drum and power to the dryer. However, after the breakers are reset, you'll still only have partial function of your dryer. For example, it might spin but not heat or it might initially turn on just to shut down after a few minutes. You must replace the defective thermal limiter to reinstate your dryer's full function.
Confirming and Replacing
Locate the thermal limiter to confirm it has blown. It's generally accessible by removing the dryer's back panel cover. Keep your dryer manual handy so you can refer to it for help if you need it. Look for a cluster of wires near the exhaust vent. The thermal limiter is the white plastic component that has two wires attached nearest to the wire cluster. If it's grey or black, the fuse has blown.
Now that you've confirmed that the thermal limiter has blown, label each wire and gently remove them from the bad thermal limiter. Reattach the new thermal limiter obtained from an appliance store to the appropriate wire, and reattach the back panel cover. Your dryer should perform normally again provided that you also addressed the reason the dryer overheated, prompting the thermal limiter to trip.
Turn off the clothes dryer's main power supply before you access the back panel cover to search for the thermal limiter. If you have a gas dryer, close its gas supply valve, too. Although changing out a thermal limiter is relatively easy to do, don't attempt it if you're uneasy about making dryer repairs. Instead, call a dryer repair technician to assist you.