PDF associated:
/ClockSpringsTech04-2005.pdf
Clock Springs The Supplemental Inflatable Restraint SIR Systems used in today s vehicles are designed to supplement the main restraint system seat belts They are designed to help reduce the severity of personal injury to the vehicle s occupants by deploying the steering wheel airbag assembly and or side air bags if equipped This system is very effective when used in conjunction with the seat belt system MAJOR COMPONENTS The major components of the system include Airbag module s Clock spring airbag coil Impact Arming Sensors Airbag Diagnostic Module COMPONENT OPERAT ION LOCATION Airbag modules consist of a folded stored airbag s located in the steering column sides of vehicle can be located in the seat back sides or the body and right front dash The clock spring airbag coil consists of an electrically conductive tape shaped into a flat coiled spring located in the steering column under the steering wheel which winds and unwinds with steering wheel rotation This clock spring coil provides the path for the electrical charge nessacary to deploy the airbag in the event of a collision Impact and arming sensors send vital information to the Airbag Diagnostic Module for monitoring and deployment operations SYSTEM OPERATION Air bag systems are self diagnostic and self monitoring All critical inputs and outputs are constantly scanned for faults opens or intermittent operation When the ignition key is cycled to the on or run position the system goes through a self check The Airbag Light will flash for approximately 8 seconds and will turn off if the system has found no faults If a fault is present open circuit resistance value not correct etc the Airbag Diagnostic Module will cause the airbag light to illuminate and stay on The system will then automatically default to off won t operate Impact sensors are strategically located in the front of the vehicle They consist of an arming sensor and several discriminating sensors The frontal impact sensors provide information to the Airbag Diagnostic Module feeding information such as direction and severity of the impact Impact sensors are threshold switches that close to complete an electrical circuit when the vehicle s impact level G force is high enough These sensors are vehicle specific and cannot be interchanged DEPLOYMENT OPERATION Rapid or sudden deceleration of the vehicle when an impact occurs causes the arming sensor sometimes called a safeing sensor contacts to close Information sent from the sensors is analyzed and a decision made by the Airbag Diagnostic Module to send an electrical charge to the airbag module s deploying the devise s Total time for the bag inflation is around 1 10 th of a second Immediately following deployment the airbag will deflate COMMON FAILURES Common airbag failures consist of broken contacts causing inoperative horn airbag and cruise control operation Clock springs can also be damaged or broken due to careless installation Failure to lock the steering wheel when servicing the steering system causes the clock spring to be wound too tight in one direction with resulting breakage of the clock spring REPAIRS Most air bag components can be serviced separately In the event of a deployment all of the air bag components will need to be replaced
