The relay J36 controls the engagement of the first additional heater coilThe relay is supplied from the fuse B38 .The relay J37 controls the engagement of the other two additional heater coils. The supply for relay arrives from the line for maxifuse PTC2, located on the battery, connector B99 .the ignition (INT/A) protected by fuse F49 of the junction unit under the dashboard B2. This supply is cut off in the case of overheating, via the safety switch l95 .Control unit M75 controls device operation: it is supplied by an igntiion-operated line (INT) protected by fuse F49 of underfacia control unit B2, and connected via the CAN line to Body Computer M1and the other network nodes.The climate control unit M75 sends the enabling signal for engaging the first resistance O25A to excite relay J36 and a signal to activate the two coils O25B at relay J36. Another dedicated signal controls activation of the first speed of air fan N85 , supplied by ignition-operated line (INT/A) of relay T8 and dedicated fuse F8 of engine bay control unit B1 - it is operated at the first speed in any case if the supplementary heating device is on. See E6020 AIR CONDITIONING.