The relay J36 controls the engagement circuit for the first additional heater coil O25; the power supply for the relay arrives from the line for fuse F74 of the additional fuse box B98.The relay J37 controls the engagement circuit for the other additional heater coil O25; the power supply for the relay arrives from the line for fuse F76 of the additional fuse box B98.The coil for relay J36 is energized by a signal for the engagement of the first resistance for O25A - from pin 12 of supplementary heater control unit M75.The coil for relay J37 is energized by a signal for the engagement of the first resistance for O25B - from pin 6 of supplementary heater control unit M75.Control unit M75 is supplied - at pin 7 - from a line protected by fuse F24 of relay T6 of B1: this ignition-operated supply (INT) is controlled from pin 1 of connector A of M1;Pin 1 of M75 is earthed.This power supply is interrupted in the event of overheating, via safety switch I95, which is also connected to pin 5 of M75.Supplementary heater control unit M75 is connected – from pins 3 and 2 - via the CAN line, to Body Computer M1 and to the other network nodes.Body Computer M1 - connector G - is supplied directly from the battery from a line protected by maxifuse F2 of engine compartment control unit B1. It is ignition-operated (INT) at pin 32 of connector D. Pin 10 of connector H of M1 supplies a reference earth to the Body Computer.When the heater is on, fan N85 is controlled from pin 4 of M75.Fan N85 si supplied from a line protected by fuse F18 of engine compartment control unit B1 and from relay T5 of B1: this is an "ignition-operated except during start-up (INT/A)" supply controlled from pin 13 of connector A of M1.