An accessory that include a machine, an input shaft, a drive member and a decoupler. The machine has a housing and a rotor that is supported for rotation in the housing. The machine effects work in response to driving rotation of the rotor. The input shaft is at least partly received in the housing. The drive member is coupled to the input shaft for common rotation and is configured to drivingly engage an endless power transmitting element to transmit rotary power between the endless power transmitting element and the input shaft. The decoupler is spaced axially apart from the drive member and couples the input shaft and the rotor in a mode that permits rotary power to be transmitted from the input shaft to the rotor in a predetermined rotational direction except when the input shaft decelerates relative to the rotor beyond a predetermined extent.