Nope never. Disconnecting the power can actually lead to an increased chance of damage. A chip that is powered up is better able to survive a static hit. Unpowered chips are much more likely to be damaged by static or random voltages. If you are worried about the computer the best thing you can do is disconnect the computer before welding. As said above keep the negative welding lead near your work.
never done that, but in the shop i used to work at we had a thing we connected to the battery, i think it was a surge protector, all i know though is the boss got pissed when i didnt use it even though nothing ever got messed up
You probably should unhook the computer. Disconnecting the battery won't really do much. All of the collision repair classes I've been to said you should disconnect the computer before welding.
With that said, I usually don't and have not fried anything yet, it really depends on how expensive the computer looks and how hard it is to get to <IMG SRC="smilies/devil.gif" border="0"> <IMG SRC="smilies/devil.gif" border="0">
when you weld it creates a magnetic field around the welding leads, at the weld and potentially anywhere on the car between the electrode and the ground cable, if the leads are close to the computer or a sensor or a lead for anything that is connected to the computer you could create problems.
For example, you're welding on the fender
and directly under the fender is an ABS sensor. Since a lot of sensors contain coils if you weld close to one it generates a charge by inductance(magnetic field passing through a coil, just how a generator works) and sends that back to the computer and POW, fried computer.
This can also happen to your stereo if you weld near the speakers and I have fried a tape deck before.
Back when I worked at a body shop I was welding a floor pan seam on a $60K Beamer with the battery conected. To my horror, the Dam thing wouldn't start for about an hour, but eventually she came around and started.
On zapping ICs, more important than having a chip "powered up", is probably
to keep them tied to ground. With the entire chassis, ground harness wires,
etc. all tied together it would seem hard to raise the potential to ESD zap
Most auto ICs are designed to be pretty robust....to take negative
12V, easily 24V, and other odd combinations. The designers have to ensure
they'll survive most any type of dual battery (jump, charge) misconnection
I think the only way to destroy your computer is to clamp your welding ground lead on it. Electron flow from welding finds the shortest path to the ground lead, if that path was through the computer, it might become a fuse. You could only induce transient voltages by welding adjacent to your 12v battery lead. The computer will have some power filtering circuits that will just pass them to ground.
Thanks for al your input fellas. I don't think I'm gonna unhook anything ever again. Haha and yes it is too hard when I could be workin on <IMG SRC="smilies/beer.gif" border="0"> and <IMG SRC="smilies/smokin.gif" border="0">
4bangr has it right....electricity always takes the path of least resistance. I've welded tons of stuff on to my frame (shock mounts, spring hangers, etc....) and have yet to disconnect the computer or the battery. The electricity flows from the welder tip through the frame (or whatever your welding..) and directly to the ground clamp, so I wouldn't worry too much about it.
I weld on tractor-trailers all the time.
This is a common topic of dicussion in my shop. The crew has a mixed bag of experiences with welding with electronics hooked up. Several have had engine ECMs destroyed due to welding. Others have had no problems. Most of us at least disconnect the batteries.
On new Freightliners, you can have as many as NINE ECMs!!! All in one tractor. It can add up to well over $15,000 in electronics, plus shop labor to replace them. And all of these ECMs are connected over a datalink. Weld too close to the datalink, and it will take them all out. Better safe than sorry.
[ 09-30-2001: Message edited by: Robert ]
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