Supplemental Restraint System (SRS)
The Supplemental Air Bag Restraint System (SRS) is designed to provide increased accident protection IN ADDITION TO that provided by the three-point safety belt system. Safety belt use is necessary to obtain the best occupant protection and to receive the full advantages of the supplemental air bag. FORD RECOMMENDS THE USE OF SAFETY BELT SYSTEMS FOR ALL VEHICLE OCCUPANTS.
The SRS consists of:
- Electrical system
- Driver side air bag module
- Passenger side air bag module
- Sensors
- Air bag diagnostic monitor
- Air bag warning indicator
- Tone generator (internal to the air bag diagnostic monitor)
The following four steps show how the air bag system works:
NOTE: Steps 1-3 take place in a fraction of a second.
1. The sensors in the vehicle detect a severe frontal impact. When at least one front or center air bag sensor and the rear air bag sensor close at the same time, electric current flows to the inflator and ignites the chemicals.
2. The chemicals then rapidly burn in the metal container. The rapid burning produces nitrogen gas and small amounts of dust. The nitrogen gas and dust are cooled and filtered during inflation of the air bag.
3. The inflating air bag splits open the trim cover. The air bag then rapidly unfolds and inflates in front of the driver.
4. After inflation, the gas empties through holes in the air bag. The air bag deflates at once.
Electrical System
The Supplemental Air Bag Restraint System is powered directly from the battery. The air bag system can function with the ignition switch in any position, including OFF and LOCK. The air bag system can also function when the driver and passenger seats are unoccupied. The electrical system performs three main functions:
- Detects impacts
- Supplies electrical power to the igniter
- Monitors the system to determine system readiness
The electrical system components include:
- Air bag warning indicator
- Wiring harness and air bag sliding contact
- Sensors
- Igniter
Sensors
WARNING: VEHICLE SENSOR ORIENTATION IS CRITICAL FOR PROPER SYSTEM OPERATION. IF A VEHICLE EQUIPPED WITH AN AIR BAG SYSTEM HAS BEEN INVOLVED IN A CRASH WHERE THE FENDERS OR GRILLE AREA HAVE BEEN DAMAGED, INSPECT THE SENSOR MOUNTING BRACKETS FOR DEFORMATION. IF DAMAGED, THE SENSOR SHOULD BE REPLACED WHETHER OR NOT THE AIR BAG IS DEPLOYED. IN ADDITION, ENSURE THAT THE BODY STRUCTURE IN THE AREA OF THE SENSOR MOUNTING IS RESTORED TO ITS ORIGINAL CONDITION.
The three air bag sensors are located at the front of the vehicle along the body chassis. Two front air bag sensor and brackets are located beneath the front fenders on the right and left front bumper cover supports. The center air bag sensor and bracket is located on the radiator support.
The air bag sensors each consist of:
- a sensing mass
- a bias magnet
- a cylindrical tube
- two electrical contacts
During normal operation, the bias magnet holds the sensing mass in place against the magnet. The two electrical contacts remain open during normal operation. Upon impact, the sensing mass pulls away from the bias magnet and rolls down the cylinder toward the electrical contacts. When the sensing mass hits the electrical contacts, it completes the air bag deployment circuit.
When the circuit is completed, it grounds the ignitor in the air bag modules and the air bags are deployed.
NOTE: At least one forward or center air bag sensor and the safing sensor must be activated simultaneously to inflate the air bags.
Unless the air bag sensor is damaged during impact, the sensing mass returns to its original position after making contact.
The safing sensor is located beneath the center console against the bulkhead. It detects the vehicle deceleration ratio in the event of a collision.
The safing sensor consists of:
- a sensing mass
- a bias magnet
- a cylindrical tube
- two electrical contacts
The design and operation of the safing sensor is much like that of the forward and center air bag sensors. The primary difference is the calibration; a safing sensor magnet is weaker than the forward or center air bag sensor magnets. The safing sensor will trigger when the vehicle crashes into a rigid barrier at approximately one or two mph.
The safing sensor ensures that, in the event of an electrical short circuit in one of the forward or center air bag sensors or wiring, the air bags will not deploy when not required.