Welding On A New Tractor

AlanB · Nov 2, 2007

jimmer2880 said:
Help me understand how unhooking the battery doesn't HELP to protect the components.

My theory (which, must be incorrect by the qty of people saying it doesn't work), is that in order for damage to occur, there must be a circuit. So, the positive & negative sides must both be connected. Kind of like how a bird can sit on a bare 10,000 volt high tension power line without getting fried. When you disconnect the battery, there is no longer a circuit (in my mind anyway).

However, of course, most items ground to the frame, so you'd have to break that connection before being completely isolated. But, how can sending positive juice through the frame make a circuit complete?

I will take a run at this, and try with the same example I used last time.

First, you have to agree that sometimes "the path of least resistance" that the electricity will take, is not always what we "think" or maybe where we "think" it is.

My next part of the illustration is to take whatever expensive peice of electronic stuff out of your car you care to think may be harmed. and hook a peice of metal to each side of it, say with a bolt, so now you have an ECM thingamaboby with a metal ear connected off each side. No wires pluged in, just too peices of steel off each side.

Now hook your ground clamp to one side and strike an arc on the other, think Voltage is passing through that electronic whatchamacalit?

Will it hurt it? Dang fine question 20 +- VDC probably not really (although I think it could), throw a little hi freq into the mix and all my bets are off.

So that is my best graphic example (second behind the muffler shop but that was already used

)

With welding we are often dealing with imperfect electrical connections, and often are not working on clean, ground, shiny smooth surfaces where everything is making good contact.

You ever jump start a car, and have to go back and wiggle the jumper cable to get it to "bite" in a little better? That would be a good example of the type connection we are making, and when they make the connection say on the block, then weld on a fender, and you later find there was no ground strap between the two, the electricity got between them somehow.

Oh, and I use a muffler shop that only uses OA. Owner told me it just removes liability.