| Marty,The risk is not from the normal voltage & the current given out by a welder during use, but instead from the very large "voltage spike" that occurs unavoidably "when the arc is switched off".This spike occurs because the high current path through the welding cables, the weld pool & the arc itself will set up a significant electromagnetic field around itself. When tgis field collapses very suddenly as the arc is switched off it will induce a voltage pulse in a nearby electrical circuts even if they are electrically isolated from the actual welding current path. The size of the pulse is determined by a whole host of factors but long connecting cables are particularly good at suffering from this induction effect, hence the need to disconnect them from sensitive circuts.The welder transformeritself also generates a big spike as its electromagnetic collapses when the arc is switched off.This is directly carried into the component being welded & so distributed to anything connected to it. some mechanics disconnect the battery during welding in the mistaken beliefthis will protect those sensitve systems on the the machines from voltage spikes. Others think that positioning the welding earth clamp nearer to the weld will offer protection. In fact neither of these methods makes any difference to the voltage spikes ability to cause irreparable damage. The only way to guarantee protection is one of three ways in order of effectiveness.(1) remove the piece to be wekded & weld it before refitting it. (2)fit a surge protection device available from the local welding vendor supplier. (3)disconnect all & every sensitive piece of equipment from long connecting cables. Having said all this, welding a machine ,or any vehicle without taking such precautions doesnt mean it will always be damaged. It does however meanyou are risking damage & given the cost of replacing the componets you have to ask yourself ,weather its a risk that is really worth taking.later...RS  |