Operation (page 2 of 3)

The alarm ECU is connected to all the door switches (including the tail door) and the bonnet switch. When the perimetric alarm system is armed, the ECU monitors the switch circuits and detects open or grounded circuit. By monitoring the circuits in this way, the alarm ECU can tell if any of the hinged panels are open or closed. The alarm ECU is connected to the following switches;

• The alarm ECU (C0061-5) to the RH front door switch (C0054-1) on a slate/white wire.
• The alarm ECU (C0061-16) to the LH front door switch (C0033-1) and the tail door switch (C0615-1) on purple/blue wires.
• The alarm ECU (C0061-16) to the RH rear door switch (C0111-1) on a purple/blue wire.
• The alarm ECU (C0061-16) to the LH rear door switch (C0112-1) on a purple/blue wire.
• The alarm ECU (C0061-9) to the bonnet switch (C0007-2) on a orange/blue wire.

When the doors and bonnet are closed, the switches are open. If any door is opened, the respective switch closes to earth through the fixings. If the bonnet is opened the switch (C0007-1) is earthed on a black wire.

For volumetric protection, when the alarm is armed, the alarm ECU (C0061-20) provides a feed to the volumetric sensor (C0719-1) on a black/brown wire. The sensor (C0719-2) is earthed on a black wire via the earth header (C0550-1). When the alarm system is armed, the volumetric sensor (C0719-3) sends a constant voltage signal back to the alarm ECU (C0061-3) on a white/black wire. If the volumetric sensor is triggered, this changes to a pulsed signal. The alarm ECU, recognising this fluctuation in voltage, triggers the alarm.

When the alarm is activated, the alarm ECU (C0057-5) provides an earth for the alarm relay (C0731-4) on an orange/white wire. Current flows across the relay switch (C0731-6 & C0731-2) and onto the alarm sounder (C0520-2) on a orange/black wire. The alarm sounder (C0520-1) is earthed on a black wire.