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Can I use a plasma cutter to cut off my bed?

Discussion in 'The Garage' started by juanblzer, Mar 11, 2003.

  1. juanblzer

    juanblzer 1/2 ton status

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    Would using a plasma cutter blow my computer? I heard that was the case. My blazer is an 85'. Anyone know?
    juan /forums/images/graemlins/grin.gif
     
  2. k5blazerus

    k5blazerus 1/2 ton status

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    you shoud be fine with the plasma cutter.Just connect the ground lead to a good ground. (correct me If I am wrong)
    Colin
     
  3. captain chaos

    captain chaos 1/2 ton status

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    what if you unhooked the battery cables, just to be safe..
     
  4. Waxer

    Waxer 1/2 ton status Author

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    Leaving the battery cables connected is actually a safer way to do it. Any ground spikes that might be encountered at the computer mounting area would be filtered if the battery cables were still connected.

    I've welded on many vehicles and always left everything connected. Keep the ground as close as possible to the work area and you will be fine.
     
  5. captain chaos

    captain chaos 1/2 ton status

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    i stand corrected /forums/images/graemlins/blush.gif

    dave
     
  6. jeffro

    jeffro 1/2 ton status

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    Unplug the brain box.
     
  7. HarryH3

    HarryH3 1 ton status Author

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    Disconnect the battery to help protect all of the electronic stuff on board. Then get up under the dash and unplug the harness from the engine computer just to be extra safe. Fire up that plasma torch and have a blast! /forums/images/graemlins/thumb.gif
     
  8. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    When I'm welding, I always try to do as Harry says. But, realistically, I've forgotten several times with no damage. Always ground really well right beside where your working. That's probably why I've gotten away with a few boo-boos. /forums/images/graemlins/blush.gif
     
  9. Waxer

    Waxer 1/2 ton status Author

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    [ QUOTE ]
    Disconnect the battery to help protect all of the electronic stuff on board. Then get up under the dash and unplug the harness from the engine computer just to be extra safe. Fire up that plasma torch and have a blast! /forums/images/graemlins/thumb.gif

    [/ QUOTE ]

    With regard to the assumption that you should un-hook the battery (as "cheap insurance"), based on the principles of electrical behavior you'd be better off (if it mattered, but it doesn't) leaving it connected so it can act as a capacitor to filter any voltage spikes. Taking the battery out of the circuit won't isolate squat.. except the battery. Ever see a car run with no battery in it?
    If you're concerned about isolating the computer unplug IT.

    Disconnecting the battery wil not do anythig towards protecting the ECM. You are inducing a spike into the GROUND side of the circuit. So, you would need to electrically isolate the module (i.e. unplug and remove) to ensure protection
     
  10. HarryH3

    HarryH3 1 ton status Author

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    You're forgetting one rule of electricity. Without a complete circuit, no current can flow. Remove the power lead from the battery and those ground spikes no longer have a path through the sensitive electronic parts of your vehicle. /forums/images/graemlins/thumb.gif
     
  11. Waxer

    Waxer 1/2 ton status Author

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    My point was they won't have a path through the electronic equipment regardless if the battery is disconnected or not.

    Electricity takes the path of least resistance. You put your ground clamp close to your work and you will have no problems with it mysteriously taking a route through the rest of the vehicle before it gets to the electrode/ground clamp depending on what you are doing and its polarity.
     
  12. HarryH3

    HarryH3 1 ton status Author

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    Nope. It actually will have a path. Due to the high frequency nature of the spikes, the voltage of "ground" can see nearly instantaneous spikes of very high voltage. Since the other side of the electronic circuits have a path to make a complete circuit, they see a short duration, high current spike where "ground" is suddenly a much higher voltage than B+.

    As for welding with everything still connected... Sometimes you get away with it. Sometimes you don't. Many years ago I worked in a semiconductor reliability testing lab. The company spent millions of dollars to find out what would cause their stuff to fail, and why. Current spikes were one failure mode, though often it took more than one occurence to create a complete failure. But using a scanning electron microsope, you could see where parts of the tiny aluminum "wires" on the chip had been blown away by a spike, even though the chip was still functional. Once damaged, it didn't take much to finish it off when the test unit was subjected to more abuse.

    Think about what happens to all the electronic stuff in a house if lightning strikes the ground or a tree nearby. It smokes it all, even though the typical path for the current is through the ground.
     
  13. Waxer

    Waxer 1/2 ton status Author

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    Very good information from this. Looks like I stand corrected and actually learned something today. /forums/images/graemlins/smile.gif

    I'm by no means an expert on anything, but I do openly share my experiences and information obtained over the years. This looks to be contrary to what I've found to be fact over the years. I will definitely take a closer look at my practices in the future.

    Thanks

    Steven
     

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