Abstract: An electromagnetically operated engine cooling fan drive assembly is disclosed having a configuration particularly suited for retrofit applications, including a central shaft adapted to be mounted to an existing fan drive flange to be driven thereby. The fan is mounted on a fan hub member rotatably mounted on the central shaft, with a temperature responsive electromagnetic clutch arrangement controlling drive to the fan hub which arrangement includes an inner body keyed to the central shaft, an armature connected by spring connection to the fan hub, and a fixed electromagnetic coil energized by a temperature switch at high engine temperatures and adapted to urge the armature into clutching engagement with the inner body and cause the fan to be rotated.