Unplug your appliance from its power supply before attempting any work on it.
Locate the access point to the thermal fuse in your appliance. Consult any user manuals supplied with your appliance to help you. In hair straighteners, the fuse is likely to be located behind a removable panel near to the switch. In a dryer, access should be possible through the front or rear removable panels. In a coffee maker, access is usually through a removable plate on the underside of the machine.
Remove the access panel and locate the fuse. Thermal fuses are small rectangular or cylindrical items made of metal or plastic, with two wires attached. They are usually mounted with screws to the body of the appliance.
Sometimes, in a portable appliance or one with moving parts, the connections can be knocked loose. Determine if the fuse is connected properly by removing the two wires using a pair of pliers and then reconnecting them. Reassemble and test the appliance. If this has not solved the problem, it is likely that the fuse has blown and needs to be replaced.
Make note of the wiring order so you can reconnect the wires properly. Disconnect the wires and remove the screws holding the fuse in place. Dispose of the old fuse.
Screw the new fuse into place and connect the wires.
Reassemble the appliance and test its operation.