To surely protect an electric circuit, even if wrong wiring is made in a wiring construction, and to restore an equipment to its essential normal operation without the accompaniment of replacement of parts within an electric circuit, when wrong wiring is recovered to normal wiring.

This protector is equipped with a ventilating fan body, a damper motor 14 for an electric damper for air supply which interlocks with the ventilation fan body, an electric circuit which is electrically connected to the ventilation fan body and the damper motor 14 by wiring, and a PTC thermistor 21 for increasing the impedance by heat generation by an overcurrent at the occurrence of overcurrent due to wrong wiring and restoring it to the normal condition by recovering the wrong wiring to the normal wiring condition, provided in the electric circuit.