A control signal output unit (62) outputs a rotational direction signal indicating a rotational direction of a motor (53) and a pulse width modulation control signal. A motor-driving unit (63) drives the motor (53) based on the pulse width modulation control signal and rotational direction signal inputted therein. A connection unit (64) electrically connects the control signal output unit (62) and the motor-driving unit (63) to transmit the pulse width modulation control signal and rotational direction signal outputted from the control signal output unit (62) to the motor-driving unit (63). The motor-driving unit (63) comprises a trouble-detecting unit (631). The trouble-detecting unit (631) successfully detects an occurrence of a trouble in the connection unit (64) by comparing the duty ratio in the inputted pulse width modulation control signal with the rotational direction in the inputted rotational direction signal.