Using a multimeter, check with the ignition key in the ON position between pins 1 and 4 and between pins 3 and 4 of the solar sensor See K090 SOLAR SENSORthat the voltage is proportional to the thermal energy present on the windscreen analyzed by the sensor photodiodes: there should be a signal of less than 5 Volt (between 4.5 V - minimum solar rays - and 0.5 V - maximum solar rays).If there is a problem, using a multimeter and disconnecting the sensor, check the sensor power supply connector [EL_K090], with the ignition key in the ON position between pins 1 and 4 and between pins 3 and 4 is about 5 Volt.