The invention relates to a control system for controlling a clutch valve (36) of a viscous clutch (32) fan system (30) comprising: a delta speed module (54) that determines one of an over speed condition, an under speed condition, and a steady state condition based on a desired fan speed (68) and an actual fan speed; a mode module (56) that determines a mode (72) of the clutch (32) based on the one of the over-speed condition (220), the under-speed condition (230), and the steady state condition (240), wherein the mode is one of a pump in mode (110), a pump out mode (130), and a closed loop mode (140); and a valve control module (62) that controls an operational state of the clutch valve (36) based on the clutch mode (72).
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