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Discharging Airbag capacitors

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  • Discharging Airbag capacitors

    Has anyone heard of discharging an airbag capacitor by touching a batteries + & - cables together?
    Has any department tried it and if so what precautions did you take.

  • #2
    If you are talking about jumping both terminals with a cable in an attempt to kill the power to the airbag capacitors...that would cause a spark...we have enough problems to deal with than have another source of ignition!

    Take care and be safe...Lt. Gonzo

    [This message has been edited by Lieutenant Gonzo (edited January 21, 2000).]


    • #3
      A Posting from Forum Moderator Ron Moore -


      There is some basis in truth for the comment about touching battery cables together. I researched this topic and found that this procedure is currently printed in the Maryland State Fire Training course on extrication. The problem is, it is WRONG!

      Here's the story. If you encountered a 1989, 1990 or 1991 Ford with a driver only airbag that is "loaded", due to the primitive design of the airbag system, you CAN drain the capacitor by unhooking both the negative and the hot cable from the battery and touching those two cable ends together. Ford reports that for the small number of vehicles made ten years ago, it did work.

      Why this procedure is wrong today is that Ford changed their system. All airbag capacitors on Fords since 1991 model year and for that matter, all other manufacturer's electrical airbag systems CANNOT be drained by doing this.

      Vehicle Electrical Shutdown Tactical Procedures-

      I. Inside rescuer/EMS responder-
      o once access is gained to passenger compartment, determine need for operation of any electrically-powered features of the vehicle and activate features as deemed appropriate
      -unlock all doors with electric door lock switch
      -lower door window glass with electrically-powered window switch(s)
      -move electrically-powered seats as necessary
      -unlock and release inside trunk release latch with electrically-powered button

      o turn ignition switch of vehicle to 'off' position if possible

      o operate inside hood release mechanism to release hood latch

      II. Outside fire/safety personnel-
      o position portable dry chemical fire extinguisher ( or equivalent) at front corner of vehicle

      o assess condition of bumper and front of vehicle and approach if safe to do so. ( If unsafe to work at front of vehicle, move personnel to side fenderwell area to access engine compartment)

      o release outside hood safety latch and open hood (If hood is jammed, forcibly open hood at latch or hinge assembly)

      o bend one hood hinge 90 degrees to maintain hood in up/open position

      o determine location of single or multiple batteries (If battery is not located in the engine compartment, determine alternate location and gain access to battery)

      o initiate hazard control activities if physical damage to battery has caused safety concern ( acid/fluid spill, fumes, open arc/sparks, fire)

      o contact inside rescuer/EMS to coordinate timing of electrical system shutdown

      III. Shutting down power at battery
      o cut negative battery cable(s) first using care not to touch any metal part of the chassis with the cable or your tools, thus minimizing risk of creating a spark

      o cut each ground cable a second time to remove a minimum 2 inch section
      ( if unbolting ground cables at battery terminal, fold cable and clamp onto itself and securely wrap with insulating tape to protect bare cable clamps from establishing a ground)

      o check that all negative grounding cables have been disconnected from the battery

      o assess if there is any evidence that power from the battery is still running any part of the electrical system of the vehicle

      o cut positive battery cable(s), also cutting each 'hot' cable a second time to remove a minimum 2 inch section

      o check the electrical system again to make sure it is not receiving power.

      o if electrical system remains energized after this action, determine location of additional batteries and repeat shutdown tactics for second battery.


      • #4
        My dept had some discusiion on this a while back. A few people seemed to think it was the proper thing to do. I have a friend who installs high end car stereos (using multiple high capacity capacitors) and he advised that shorting the + and - cables together on a car with theses capacitors would result in a rather large spark. These capacitors are usually in the trunk out of site so you wouldn't know they were there.
        I personaly never short the cables, but there are others who do. Your better off using a restraint system.

        David Brooks, Firefighter, D/O, 1st Resp.
        Newmarket Fire & Rescue
        Newmarket, New Hampshire


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