A system includes a retarder in electrical communication through an electric link with an alternator, and a controller that compares a power measurement with an accessory load on a system during a retard event, and can reduce an electrical load on the alternator, or can remove all electrical loads from an engine, when electric power that is generated from the retarder is measured to be greater than an accessory load on the system. The system may include an alternator that provides a motor function to rotate a shaft coupled to an engine that is mechanically coupled to one or more mechanically drivable accessories. The alternator powers the mechanically drivable accessories in place of or in addition to the engine.