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Jerky seat belt pretensioner

Discussion in 'Gen 2 Prius Audio and Electronics' started by Sherman39, Mar 24, 2005.

  1. Sherman39

    Sherman39 New Member

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    I recently installed my own CD/MP3 deck using the stock speaker wires and paralleling power from the stock radio. On a recent trip I noticed that the seat belt tended to infrequently tug and then release, perhaps an inch or so.

    The other thing that had changed on the vehicle was I had a portable DVD player going for the children in back.

    Commuting today, I didn't notice this effect.

    The owner's manual warns against audio changes interfering with safety systems. Any advice? The car is an '02.

    Thanks very much,
    Chuck Emblen
    [email protected]
     
    #1 Sherman39, Mar 24, 2005
  2. DanMan32

    DanMan32 Senior Member

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    What many don't realize, is the pretensioner is a self sacrificing explosive device that sends an impact to tighten the seatbelt. It activates with the airbags. I doubt you affected this. At least you won't know it until you need it.

    Seatbelts also employ some sort of lock that is not self sacrificing. In old days, the seatbelt would lock until it was retracted all the way, then you could pull it out. Many today lock using an acceleration lock. When the car rapidly reduces acceleration, the seatbelt would lock. Some do this mechanically, some electrically. Some that do this electrically link it with the brakes.
    The qestion is if the lock is mechanical, in which case you couldn't have done anything, or electrical. If electrical, you would have had to cut a wire or something.
     
    #2 DanMan32, Mar 24, 2005
  3. HTMLSpinnr

    HTMLSpinnr Super Moderator
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    On my '02, the tensioner would frequently jerk upon turning the car off. There is an additional electronic device along with the explosive device on that model. I asked the dealer about it, and they claimed it was normal (as his 4'Runner did it too) at the time.

    I'd suggest rerouting the cables to make sure you're not inductively causing the device to trigger.
     
    #3 HTMLSpinnr, Mar 24, 2005
  4. Sherman39

    Sherman39 New Member

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    Dan - Rick

    Thanks a ton for your responses! I had read that the pretensioner was an explosive device. It's good to know now that there is an active tensioning system as well. Isn't it great that even after the advent of the air bag, progress continues on seat belts? Active tensioning, pretensioner, force limiting..

    I'll take a look at those harness routings.

    My Prius is project heaven right now: CD Deck, speakers, factory cruise kit, bike hitch,...Of course I can justify it all due to the gas savings...

    Regards,
    Chuck Emblen
     
    #4 Sherman39, Mar 24, 2005
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