and remains connected between the first external connection terminal 102 and the fixed contact 108 however under second abnormal overload conditions such as when the contact mechanism of first bimetal 116 fails and an overcurrent flows the resistance heat of the auxiliary bimetal 12 and the amount of the resistance heat of the surrounding conductors such as the fixed contact 108 etc become significant so that the temperature of the auxiliary bimetal 12 rises and the solder 16 melts when bimetal 12 is heated to its snap action temperature approximately 200 degrees centigrade the auxiliary bimetal 12 snaps and is displaced with the lower part 12b of the auxiliary bimetal 12 being separated from the fixed contact 108 and contacts thermoplastic resin member 14 which is across from it the thermoplastic resin 14 has already been softened and the lower part 12b of the auxiliary bimetal 12 becomes at least partly buried in the resin in this second abnormal overload condition the separation of the auxiliary bimetal 12 from the fixed contact 108 shuts off the electric current and protects the load even in the case of failure mode problems with contacting mechanism when the electric current is shut off as described above for second abnormal overload condition neither the auxiliary bimetal 12 nor the other conductor continue to produce heating and the thermoplastic resin member 14 is gradually cooled and hardens with the auxiliary bimetal 12 being buried therein that.