at a hard mode position when the electromagnets 178 and 180 are energized fig5 shows a circuit diagram of the first embodiment of a driver circuit for selectively energizing the electromagnets 174 176 178 180 182 and 184 for controlling the position of the rotary valve 66 in order to selectively energizing the electromagnets 174 176 178 180 182 and 184 a manually operable mode selector switch 198 is provided in the driver circuit in the shown embodiment the mode selector switch 198 is operable between a soft mode position a medium mode position and a hard mode position the mode selector switch 198 is disposed between a vehicular a power source and the actuator which composed of the electromagnets 174 176 178 180 182 and 184 the power source includes a vehicular battery 200 a main witch 202 such as an ignition switch and a fuse 204 the actuator 100 has three input terminals 206 208 and 210 the terminal 206 is connected to a soft mode terminal 212 to be connected to the power source via a soft mode contactor 218 the terminal 208 is connected to a medium mode terminal 214 which is in turn connected to the power source via a medium mode contactor 220 the terminal 210 is connected to a hard mode terminal 216 of the mode selector switch which hard mode terminal is connected to the power source via a hard mode conductor 222 the actuator 100 also has a grounding terminal 224 which is commonly connected.