General Description
The Supplementary Restraint System (SRS) has been specifically designed to protect the driver and passenger from sustaining severe facial and upper body injuries in the event of a serious impact. Full protection can only be ensured when used in conjunction with a conventional three point safety belt; the seat belts form an integral part of the Supplementary Restraint System (SRS).
The visible VIN plate shows the air bag symbol.
WARNING: ALL VEHICLES EQUIPPED WITH THE PASSENGER AIR BAG FROM THE FACTORY HAVE A WARNING STICKER ATTACHED TO THE INSTRUMENT PANEL PROHIBITING THE USE OF REAR FACING CHILD OR BABY SEATS.
It is not possible under any circumstances to disable the passenger air bag while maintaining the integrity of the whole system.
The system consists of:
^ Air bag diagnostic monitor
^ Wiring harness
^ Air bag sliding contact
^ Air bag indicator
^ LH and RH crash sensors
^ Safing sensor
^ Air bag module(s)
^ Mechanical seat belt pretensioners
The air bag diagnostic monitor performs system checks and continually monitors the system during normal operation. The air bag diagnostic monitor does not have any deployment function. In the event of a fault being detected the air bag indicator is illuminated either constantly or intermittently.
If the bulb fails, the air bag diagnostic monitor will emit an audible warning ONLY if a fault is detected. If the bulb fails to illuminate, repair the system.
The air bag indicator is located in the instrument cluster. It illuminates for approximately six seconds when the ignition is turned ON then will go OFF unless a fault is detected.
The sections of wiring harness which carry air bag wiring are marked by yellow insulation to aid identification of air bag wiring harness routing.
The sliding contact is designed to carry signals between the air bag diagnostic monitor and the driver's air bag module. The sliding contact is attached to the steering column switch mounting bracket and consists of fixed and moving parts connected by a coiled Mylar tape with integral conducting tracks. The Mylar tape is able to 'wind up' and 'unwind' as the steering wheel (to which the moving part is attached) is turned, maintaining electrical contact at all times between the air bag diagnostic monitor and the air bag module. The sliding contact is used in order to achieve the high degree of circuit integrity required by the Supplementary Restraint System (SRS).
The driver and passenger air bag modules consist of the following components which cannot be disassembled:
^ Inflator
^ Bag
^ Container
^ Cover
The inflator is screwed into a metal cup-shaped container. The bag is then folded on top of the inflator and the whole subassembly is closed by the cover.
The driver air bag module is attached to the steering wheel, the cover forming the outer surface of the steering wheel boss. The cover has invisible 'split lines' moulded in its surfaces allowing the air bag to easily exit though the cover when the system deploys.
The passenger air bag module is located above the glove compartment and is integrated into the instrument panel to provide an unobtrusive appearance. The cover is a one piece moulding held by five clips and a short retaining strap. As the air bag deploys, the cover is forced free of the clips, but remains attached to the instrument panel by the short retaining strap.
The purpose of the inflator is to generate the gas needed to fill the air bag. It consists of a high strength steel casing filled with a solid propellant charge and an electrically activated igniter. The igniter is activated when the safing sensor closes the deployment circuit, which in turn ignites the propellant charge. The very rapid burning of the propellant produces sufficient gas to fill the air bag(s). As the gases expand they cool, preventing heat damage to the bag. The driver air bag module has one inflator and bag, with a filled volume of 30 liters. The passenger air bag module has two inflators and bag having a filled volume of 60 liters.
The air bags are a one-piece woven item with a silicon coating to provide flame and heat protection in the vicinity of the inflator. The shape of the passenger air bag is tailored to the vehicle proportions.
Crash sensors are mounted to either side of the radiator panel.
Each sensor contains:
^ Sensor mass
^ Bias magnet
^ Cylindrical tube
^ Electrical connector
Upon at least a 3/4 frontal impact, the sensing mass breaks away from the bias magnet and rolls along a cylinder towards the electrical contacts. If the deceleration is above a predetermined limit the sensing mass will bridge the electrical contacts completing the primary deployment circuit.
The mounting and orientation of the right-hand and left-hand crash sensors is critical to maintain correct system operation.
CAUTION: If a vehicle equipped with an air bag system is involved in a crash where the front fenders or radiator grill have been damaged,thoroughly inspect the crash sensor mounting brackets for deformation. If any damage is visible, the body structure in that area must be resorted to its original condition.
The safing sensor is mounted at the base of the A-pillar.
The safing sensor consists of:
^ Sensor mass
^ Bias magnet
^ Cylindrical tube
^ Electrical connector
The design and operation of the safing sensor is much like that of the crash sensors, the main difference being the sensor calibration. The safing sensor bias magnet is marginally weaker than that of the crash sensors.
It also ensures that in the event of an electrical short circuit in the system that the air bag modules DO NOT deploy.
When the safing sensor senses an impact above its predetermined limit the sensing mass breaks away from the bias magnet rolling down the cylinder towards the electrical contacts completing the deployment circuit. Provided its movement is simultaneously matched by either of the crash sensors the deployment circuit is closed triggering air bag deployment.
Provided the sensors are not damaged during an impact the bias mass will return to its original position against the bias magnet.
The air bag system retains a direct independent battery feed which allows the system to retain sufficient voltage to deploy the air bag modules should battery or ignition power be lost during an impact, maintaining a constant state of readiness.