To provide a method and a device for detection of trouble which can simply and surely inform a user of the alarm of a fan trouble, based on the fan on signal that the controller of a power source part for fan drive and the current of the power source for fan rotation and fan drive.

A controller 13 monitors the fan on signal of a power controller 14 and monitors the rotation of a fan 11 when it detects that signal. When the controller detects the signal of a revolution detector 12 showing the number of revolutions of a fan to be zero or its stoppage, the controller judges that there is trouble in the fan and generates a trouble signal. Moreover, when the controller detects the signal of the revolution detector showing that the number of revolutions of the fan is stationary one or that the fan is in revolution, the controller monitors the current of a power source 15 for drive, and when it detects the signal of the current detector 16 showing that the current value deviates from the one at stationary operation or that the power is off, it judges that the fan trouble occurs and generates a fan trouble signal to outside.