You'll have to disassemble it and trace wiring from power cord to switch and heating element. Inline may be a thermal fuse protecting against overheating. It's a small aluminum cylindrical device with markings, inline with the hot wire from the switch. Using a digital multimeter, a resistance check should show continuity. When overheated, this thermal fuse opens to kill power to the heating element. Replacement rated thermal fuses from electronic distributors.