2582347 - 5580C AIR BAG SYSTEM

The diagram below illustrates the Air Bag system components
The Safety Retention Systems are specially designed to work in a particular make and model of vehicle. They should therefore not be tampered with, adapted or installed on other types of vehicle, but only on the one for which they have been designed and manufactured. Any attempt to reuse, adapt or install them on a different type of vehicle could cause serious or fatal injury to the occupants of the vehicle either during normal usage or the vehicle or in the event of a crash.
in order for the safety retention system to work as efficiently as possible, the occupants must wear the seat belts, with pretensioners, correctly.
1 pretensioners2 driver''s Air Bag3 passenger Air Bag4 side bag5. control unit6. R.S.U. satellite units7. passenger Air Bag disabling switch8 failure warning light9 passenger Air Bag inhibitor warning light10 line K connector

One single control unit manages all these systems:

  • SEAT BELT PRETENSIONER SYSTEM
  • SIDE BAG SYSTEM
  • DRIVER''S AIR BAG SYSTEM
  • PASSENGER AIR BAG SYSTEM (single or dual)

Control units for TRIM LEVEL VERSIONS

Each control unit has an idenfication label. The following control units are available:

  • A.C.U.3-C03 control unit which manages the front pretensioners / driver''s Air Bag.
  • A.C.U.3-C05 control unit which manages the front pretensioners / driver''s Air Bag / passenger Air Bag.
  • A.C.U.3-R07 control unit which manages the front pretensioners / Driver''s Air Bag / passenger Air Bag.
The operation of the system for the vehicle in question depends solely on the type of electronic control unit used.The A.C.U3-R07 control unit is assisted by two satellite units or negative transverse acceleration (or deceleration) sensors. The positive and negative acceleration sensors send a signal to the control unit. The control unit records deceleration and commands the priming of the pyrotechnic charges.All the A.C.U3 control units manage the accumulation of energy for the front bags and memorize both fault codes and crash codes. The operation of the red warning light in the instrument panel is intelligent.The control unit only has to be replaced after the pretensioners or the Side Bags have been activated three times.The control unit must always be replaced if the front Air Bags are activated.

DESCRIPTION OF CONTROL UNIT FASTENING

The position the AIR BAG control units should be fitted in is shown by an arrow and MUST be observed.
The arrow should be pointing towards the front of the vehicle.
Before replacing the control unit, make sure that the new one is compatible by checking the design number on the label.Fit the bolts and tighten them in order the illustrated in the diagram. All the bolts should be tightened, in order, to a torque of 6.4 - 9.6 Nm to ensure that the control unit is correctly secured to the bodyshell.

AIR BAG CONTROL UNIT CONNECTORS

The control unit connectors are the twin wire 2 x 24 pin AMP type with 12 short circuit bars. There are 3 types of connector, one for each version of control unit, with different colours and different mechanical foolproof polarity:

  • CONTROL UNIT ACU3-C03 = BLACK CONNECTOR
  • CONTROL UNIT ACU3-C05 = BROWN CONNECTOR
  • CONTROL UNIT ACU3-R07 = ORANGE CONNECTOR

SEAT BELT PRETENSIONER SYSTEM

Cross section of pretensioners before and after activation
1 Ring gear2 Ring gear3 Toothed bush4 Rack piston5. Pyrotechnic charge6. PropellantA. Before activationB. After activation

COMPOSITION

This system consists of inertia reel front seat belts with electrically controlled, pyrotechnically activated pretensioners. The negative acceleration (or deceleration) electronic sensor is located inside the control unit which manages the intelligent warning light.The pyrotechnic activation system is an integral part of the reel and thereby creates a single component which is fitted to the vehicle pillar.
The position of the centring pin must be correct when fitting the pretensioner and the tightening torque should be betweenm 36 and 44 Nm.The position of the fastening on the centre tunnel in the passenger compartment must be correct when fitting the control unit and the tightening torque should be between 6.4 and 9.6 Nm.

OPERATION

The moment a longitudinal negative acceleration (or deceleration) of sufficient magnitude takes place, an electro-mechanical sensor in the control unit records this condition and sends a command from pins 21-22, via the power circuit, to the driver''s pretensioner and from pins 23-24 to the passenger pretensioner.The electrical control primes the gas generator pyrotechnic charges (5).The burning of the propellant (6) produces a chemical reaction creating (inert) gas whose pressure creates a force which thrusts the rack pinion (4) upwards.The upwards movement of the rack pinion (4) rotates the ring gear (1) which is connected to the ring gear (2). The ring gear (2) meshes with the toothed bush (3) changing the rotary movement of the spindle to the opposite direction to the unwinding of the seat belt, rewinding it by several centimetres.
After each impact which sets off the pretensioner, the belts can no longer be used and must be replaced.

CONTROL UNIT AUTO-TEST

The warning light in the instrument panel comes on at the Key on for about 4 secs. to indicate the control unit and warning light autotest.After 4 seconds the control unit carries out the continuous diagnosis of the system.

The AIR BAG failure warning light remains on after the 4 seconds of the check stage when:

  • the control unit is not connected
  • one of the two pretensioners is not connected,
  • the supply voltage is interrupted,
  • a fault is detected in the two seconds after the check stage.
The vehicle should never be handed over to the customer with the failure warning light on.the earth lead is a dedicated cable and should never have couplings and/or shunts of any type between pin 5 of the control unit and the bodyshell stud; the cable length should be £ 200 mm.
The resistance between the vehicle''s electrical earth and pin 11 of the control unit must be R £ 100 mW

DRIVER''S AIR BAG SYSTEM

The diagram below illustrates the driver''s Air Bag system components.
1 Electronic control2 Clock spring3 Air Bag electrical connection4 Horn electrical connection5. Safety device6. Cover7. Bag8 Bag retaining ring9 Gas generator10 Housing11. Nuts

COMPOSITION

The driver''s Air Bag system consists of:

  • Cover
  • Bag
  • Gas generator
  • Clock spring
  • A.C.U3 control unit
A housing containing the following is fastened to the steering wheel: the pyrotechnic device with gas generator and folded bag, a cover with a pre-breakage area to facilitate the escape of the bag. In the lower part, between the steering whel and the lights switch unit, there is a clock spring which guarantees the electrical connection between the steering wheel and the A.C.U3.

OPERATION

All the components inside the control unit are subject to autodiagnosis.

The control unit also diagnoses the functions and parameters listed below:

  • BATTERY voltage,
  • satellite sensors (where fitted),
  • the electrical part of the pyrotechnic charges depending on the configuration of the system.
Incorrect configurations are detected as an open circuit, if the number of components is below the number planned. If the number is higher, this is not possible because the components which make it possible to diagnose the additional lines are missing.The control unit is equipped with a special condenser, capable of storing an energy reserve to be used for operating the front Air Bag pyrotechnic charges.This reserve energy is available for around 200 ms. from the possible electrical supply failure due to a collision and the consequent disconnection of the battery or short circuit.The pretensioners and the Side Bags (protecting the head and chest) are supplied directly and there is no reserve energy in the control unit for these devices.The auto diagnosis is activated at each Key on for a time of @ 4 s.At the same time the control unit lights up the warning light and if, after having carried out the check, no faults are detected, the warning light goes out.At the time of a collision of a sufficient magnitude, the control unit can record both longitudinal or transverse acceleration or deceleration by means of the accelorometers.When figures are recorded above the pre-set level in the control unit map, the pretensioners and later the driver''s and passenger front Air Bags are activated.

COMPOSITION

The passenger Air Bag system consists of:
1 Dual bag2 On warning light3 On switch4 Pyrotecnic charges (2)5. A.C.U3 control unit

COMPOSITION

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COMPOSITION

The enabling / disabling of the passenger Air Bag is determined by the switch on the right hand side of the dashboard.The switch is activated with the key in the ignition.The passenger Air Bag control unit (A.C.U3-C05 or A.C.U3-R07 depending on the version) should record a resistance value of 95 - 105 O for the enablement.For disablement, the resistance value should be 380 - 420 O.

OPERATION

At the key on and during the first 4 - 6 seconds, the A.C.U3 control unit tests the inhibitor switch.If the resistance value is @ 100 O (bag ON), the control unit prepares for the operation of the passenger Air Bag.If the resistance value is @ 400 W (bag OFF), the control unit prepares for non-operation of the passenger Air Bag.The passenger Air Bag ON/OFF condition can be easily recognized by the operation of the special warning light in the instrument panel.With the switch ON, the warning light flashes for 4 seconds after the 4 seconds of the test at Key on (all O.K. warning light off).With the switch OFF, the warning light remains on after the test at Key on.If the inhibitor system is broken, the error and the inhibition state are recorded, the failure and inhibitor warning lights are on constantly and only the passenger Air Bag will not be activated in the case of a crash because the driver''s Air Bag and pretensioners will be.If, after a key on with the ignition switched on, the user changes the status of the switch, the control unit records this as a plausibility error causing the failure and inhibitor warning lights to come on.The passenger Air Bag will not be activated when required.If the inhibitor warning light is broken or the enabling/disabling signal is outside of the operating range, the passenger Air Bag will automatically be disabled by the control unit.

Transferring failure warning light operation to disabling warning light

If the Air Bag system failure warning light is broken (LED or bulb burnt out), the control unit will inhibite the operation of the system and, at the same time, will switch on the disabling warning light at a frequency of 4Hz to signal the failure warning light fault.
The vehicle should never be handed over to the customer with the failure warning light on.the earth lead is a dedicated cable and should never have couplings and/or shunts of any type between pin 5 of the control unit and the bodyshell stud; the cable length must be £ 200 mm.
The resistance between the vehicle''s electrical earth and pin 11 of the control unit must be R £ 100 O

SIDE BAG SYSTEM R.S.U. SATELLITE SENSORS (Remote Side Sensing Unit)

The diagram below illustrates the SIDE BAGS.
A. Side BagB. Side impact satellite sensor1 Sensor signal2 Sensor earth

COMPOSITION

The SIDE BAG modules are fitted on the door side of the front seat backrest with the module cover in view.

The module consists of the following components:

  • a bag.
  • a gas generator which incorporates the studs for fixing the module.
  • a pin for connecting the earth.
  • a casing for housing the parts mentioned above together with the cover.
  • a cover.
The satellite sensor container is made from an insulating material with the connector incorporated.The satellites have a centring pin to ensure that they are correctly positioned; this pin is fixed in the threaded opening in the bodyshell centre pillar.The A.C.U3-R07 manages the entire system.The control unit and the satellite sensors MUST be fixed in the correct position. The sensor centring pin should be correctly inserted in the opening in the pillar.The satellites should be installed with the connector facing the floor of the vehicle.The satellites are fastened to the base of each centre pillar, one on the right side and one on the left side and tightened to a torque of 6.4 - 9.6 Nm.
The position of the sensors is defined during the design stage to ensure the optimum detection of a side impact so their position should not be altered.

OPERATION

At the KEY ON, the control unit supplies pin 2 of the side sensors and they initiate the auto-test operation.The sensors conclude the
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