The heated rear windscreen and door mirror defrosing resistances coils are activated by a specific button in the switch unit in the middle of the dashboard.The defrosting circuit is protected by a specific fuse and controlled by a relay in the junction unit under the dashboard.The control is then deactivated in two ways:- MANUALLY: pressing the same button again;- AUTOMATICALLY: after 20 minutes effective operation, i.e. with the control activated.The automatic operation of the rearscreen is linked to the engine speed.The on/off logic is as follows:- the first ten minutes of operation are independent of the operation of the engine;- the following minutes, on the other hand, depend on the operation of the engine, namely: if the number of revs is less than 1000 rpm for a period of ten seconds the heated rear windscreen is switched off, otherwise if the engine speed is more than 1000 rpm, it remains on until it has been on for twenty minutes.If the battery voltage goes below 8.5 V, the heated rear windscreen control relay switches the circuit off.