Abstract: An electronically-controlled viscous fan drive in which the output drive to the fan is electronically controlled by the movement of viscous fluid from a fluid reservoir and into the operating and working chamber of the coupling during normal operation. A radially balanced valve disk coupled to a spring controls the relative movement of viscous fluid from a fluid reservoir to the working chamber by sealingly engaging and disengaging a fill hole fluidically coupling the fluid reservoir to the working chamber. The clutch plate and cover and body, along with the features defined between the clutch plate and cover and body are cast to the desired size and shape, therein allowing easier and more precise manufacturing and more cost effective manufacturing as compared with traditional designs that are stamped and having machined-in features.