A control system for a fan of a cooling system of an internal combustion engine
of a motor vehicle having a viscous coupling (fan clutch) driving the fan and a
control unit (PID governor) to which the setpoint temperature and the measured
actual temperature of the cooling system (coolant temperature) are fed. The control
unit (PID governor) is connected downstream to a limiter, which holds the ratio
of output speed to input speed below a specifiable limit (x % of input speed).
An overheat protection logic disables the limiter when the actual coolant temperature
exceeds a specifiable critical temperature that is higher than the setpoint temperature
of the control unit (PID governor).
