VGLA - System Overview

Alarm Unit







- Only additional components, over and above those included in the central locking system.
- All cars fitted with alarms have remote controls, monitoring of doors - bonnet - boot/tailgate, relay for electronic start prevention plug, and horn or alternatively a siren. Other components are standard/optional /accessories depending on the market.

Components - input signals
- Bonnet switch (= microswitch in left bonnet lock).
Signal if the engine bonnet is open or closed.
- Control module for blower motor extended blowing time (drying of evaporator).
Signal if the blower motor is running.


NOTE! Not standard, only available for retrofitting ('service solution').


- Glass break sensor (on passenger side by the glove compartment/speaker).
Transmits a signal to the VGLA control module at the sound of breaking glass.
- Ultrasound sensors (in both B-pillars).
Transmit a signal to the VGLA control module if movements are detected inside the car.
- Metal wire inserted into the three rear windows.
Standard on 5-door cars with factory fitted glass break and/or ultrasound sensors.
Breaks an earth circuit for the VGLA control module if any window is broken (= the wire breaks).
- Level sensor (under the passenger side of the dashboard on AWD, in rear right wheel house on other cars).
Transmits a signal to the VGLA control module if the car's level changes, e.g. if the car is lifted for towing away.

Components - control signals
- Glass break sensor, ultrasound sensor, level sensor and siren.
Control signals to connect/disconnect the components.
- Horn (on engine compartment fire wall) alternatively a siren (in front right wheel housing).
Control signal to activate horn/siren. The horn is controlled via a relay whilst the siren has integrated electronics.
- Start relay, earth connection via VGLA control module.
The relay is only connected to earth if the alarm is deactivated and the ignition is on (position II/III).

Control module for blower motor extended blowing time (drying of evaporator)
- If the A/C compressor has been activated for more than 4 minutes and the ignition is switched off the control module waits for about 50 minutes and then activates the blower motor for about 5 minutes.
This function is intended to dry out any condensed water and thereby prevent bad smells.
- When the fan is running the air inside the car moves, this affects the ultrasound sensors and can trigger false alarms. A signal is therefore sent to the VGLA control module when the fan has been activated. During this time the VGLA control module ignores signals from the ultrasound sensors.

Glass break sensor
- Consists of a control module and a microphone.
- The control module is tuned into the frequencies of breaking glass. If it 'hears' this sound it transmits a signal to the VGLA control module.
- The glass break sensor control module communicates serially with the VGLA control module.

Ultrasound sensors
- Each sensor consists of a control module with two integrated transmitters/receivers (transducers). One of the transmitters/receivers is directed towards the front and the other towards the back.
- The sensors transmit sound-waves of a certain frequency and read the frequency of the sound-waves that bounce back.
If there are any movements inside the car the difference between the frequency transmitted and received changes.
When one of the sensors notices this change it transmits a signal to the VGLA control module.
- The sensors are very sensitive and will react to air movement. In order to avoid false alarms it is therefore important:
- for windows and sunroof to be closed.
- that no objects that can move are left in the car (e.g. streamer).
- the sensors are disconnected if for example a dog is left in the car or if a petrol-driven parking heater is used.
- The control modules for the ultrasound sensors communicate serially with the VGLA control module.

Level sensor
- The same level sensor design that has been introduced for Guard Alarm 2.2 (III).
- The level sensor consists of a control module and two disc capacitors lowered into an insulating liquid.
When the level of the car changes, the position of the liquid in the sensor changes leading to a change in the capacity of the disc capacitors. If the control module detects a change (e.g. the car rocks) it ignores it, but if the level change is repeated it transmits a signal to VGLA control module.
- To avoid false alarms the level sensor should be disconnected the car when is transported by lorry, train or ferry.
- The control module for the level sensor communicates serially with the VGLA control module.

Siren
- The siren has an in-built control module and back-up battery. The battery is charged automatically when the ignition is on.
- If the wiring to the siren is broken or if the voltage drops quickly (e.g. the battery is disconnected) when the alarm has been activated the siren will sound. The siren will sound for as long as the in-built battery lasts (about 5 minutes if the battery is fully charged). If on the other hand the alarm has not been activated then nothing happens.

The siren's control module communicates serially with the VGLA control module.