Ford Aerostar 1986-1997 Repair Guide

General Information


See Figure 1

The Supplemental Restraint System (SRS or Air Bag), is designed to provide additional protection for the driver in addition to that which is provided by the use of a seat belt.

The system is made up of two basic systems. They are the air bag(s) and the electrical components made up of the impact sensors, backup power supply and electronic air bag diagnostic monitor assembly.

Special attention should always be applied when working on a vehicle equipped with an air bag. If for any reason the indicator light in the dash should come on, consult an authorized dealer immediately for complete diagnostic service.

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Fig. Fig. 1: Air bag warning labels


The Supplemental Restraint System (SRS or Air Bag) provides increased protection for the driver and/or passenger in the event of an accident. The word "supplemental is key, as the air bag is designed to be used in addition to the seat belts. In the event of an accident, the air bag will be the most effective if the vehicle's occupants are held in position by the seat belts.


The air bag system consists of two subsystems: the air bag(s), and the electrical system, which includes the impact sensors and electronic diagnostic monitor.

For removal and installation procedures, refer to the Steering Wheel coverage in Suspension & Steering .

Air Bag Module

See Figure 2

The air bag module consists of the inflator, bag assembly, a mounting plate or housing, and a trim cover.

The air bag module components cannot be serviced. The air bag module is only serviced as a complete assembly.

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Fig. Fig. 2: Steering wheel, sliding contact and air bag module


Inside the inflator is an igniter. When two or more impact sensors detects a crash and the sensor contacts close, battery power flows to the igniter, which then converts the electrical energy to thermal (heat) energy, igniting the sodium azide/copper oxide gas inside the air bag. The combustion process produces nitrogen gas, which inflates the air bag.


The air bag itself is constructed of neoprene coated nylon. Fill volume of the air bag is 2.3 cubic feet.


A mounting plate and retainer attach and seal the air bag to the inflator. The mounting plate is used to attach the trim cover and to mount the entire module to the steering wheel or dash panel, depending on which side of the vehicle the air bag is mounted.


When the air bag is activated, tear seams moulded into the trim cover separate to allow the air bag to inflate.

Diagnostic Monitor

See Figure 3

The diagnostic monitor continually monitors all air bag system components and wiring connections for possible faults. If a fault is detected, a code will be displayed on the air bag warning light, located on the instrument cluster.

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Fig. Fig. 3: Air bag diagnostic monitor

The diagnostic monitor illuminates the air bag light for approximately 6 seconds when the ignition switch is turned ON , then turns it off. This indicates that the air bag light is operational. If the air bag light does not illuminate, or if it stays on or flashes at any time, a fault has been detected by the diagnostic monitor.

Performing system diagnostics is the main purpose of the diagnostic monitor. The diagnostic monitor does not deploy the air bags in the event of a crash.


See Figure 4

The sensor is an electrical switch that reacts to impacts according to direction and force. It can discriminate between impacts that do or do not require air bag deployment. When an impact occurs that requires air bag deployment, the sensor contacts close and complete the electrical circuit necessary for system operation.

Four crash sensors are used on air bag equipped Aerostar vehicles: a dual crash and safing sensor located at the hood latch support, a crash sensor at each of the right and left fender aprons, and a safing sensor at the left-hand cowl side in the passenger compartment.

At least 2 crash sensors, one safing and one front, must be activated to inflate the air bag.

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Fig. Fig. 4: Cutaway of air bag sensor


Always wear safety glasses when servicing an air bag vehicle, and when handling an air bag.
Never attempt to service the steering wheel or steering column on an air bag equipped vehicle without first properly disarming the air bag system. The air bag system should be properly disarmed whenever ANY service procedure in this guide indicates that you should do so.
When carrying a live air bag module, always make sure the bag and trim cover are pointed away from your body. In the unlikely event of an accidental deployment, the bag will then deploy with minimal chance of injury.
When placing a live air bag on a bench or other surface, always face the bag and trim cover up, away from the surface. This will reduce the motion of the air bag if it is accidentally deployed.
If you should come in contact with a deployed air bag, be advised that the air bag surface may contain deposits of sodium hydroxide, which is a product of the gas combustion and is irritating to the skin. Always wear gloves and safety glasses when handling a deployed air bag, and wash your hands with mild soap and water afterwards.

For removal and installation procedures, refer to the Steering Wheel coverage in Suspension & Steering .


  1. Disconnect the negative battery cable.
  3. Disengage the electrical connector from the backup power supply.

The backup power supply allows air bag deployment if the battery or battery cables are damaged in an accident before the crash sensors close. The power supply is a capacitor that will leak down in approximately 15 minutes after the battery is disconnected, or in 1 minute if the battery positive cable is grounded. It is located in the instrument panel and is combined with the diagnostic monitor. The backup power supply must be disconnected before any air bag related service is performed.

  1. Remove the nut and washer assemblies retaining the driver air bag module to the steering wheel.
  3. Disconnect the driver air bag module connector and attach a jumper wire to the air bag terminals on the clockspring.
  5. Connect the backup power supply and negative battery cable.


For removal and installation procedures, refer to the Steering Wheel coverage in Suspension & Steering .

  1. Disconnect the negative battery cable and then the backup power supply.
  3. Remove the jumper wire from the air bag terminals on the clockspring assembly and reconnect the air bag connector.
  5. Position the air bag assembly.
  7. Connect the backup power supply and negative battery cable. Verify that the air bag light illuminates when the ignition switch first is turned ON .