SYSTEM FOR CONTROLLING A MEANS FOR THE THERMAL REGULATION OF A MOTOR VEHICLE ENGINE COOLING CIRCUIT AND METHOD OF CONTROLLING SAID CONTROL SYSTEM

System for controlling a means for the thermal regulation of a motor vehicle engine cooling circuit and method of controlling said control system. System for controlling a means (8) of thermally regulating a cooling fluid circulating in a cooling circuit (2) of a motor vehicle internal combustion engine (3), the said means of thermally regulating the fluid comprising a fluid inlet (8a) connected to an inlet for cooling fluid leaving the engine (3) and a first, a second and a third fluid outlet (8b, 8c, 8d) which are respectively connected to a first branch (2a) containing a radiator (5) for cooling the engine, a second branch (2b) containing an engine-oil fluid exchanger (7) and a third branch (2c) containing a unit heater (6). The control system comprises a module (13) for determining the mode of operation, summer mode or winter mode, of the thermal regulation means and a module (16) for controlling the opening or closing of the third branch (2c) according to the temperature (T_fm) of the fluid leaving the engine and the temperature (T_fa) of the fluid upstream of the unit heater.