I have used a surge protector and so far have had no trouble, but sometimes if working on site and don’t have one I have disconnected the battery or alternator. I have also just gone ahead and welded the machine without taking any precautions and to press I have been lucky, I know it’s not ideal.There is some feeling that the surge protectors are not really up to protecting all modern sophisticated electrical systems and you should not rely on them and the only sure way is to remove any ECU's/computers completely.I think the harm can be done when you strike the arc and remove the arc and with the surge of EMF being created and then rapidly falling off this can play havoc with the electrics.We have been taking about this issue at work and it is one of those things that the more you think about the more worried you get, because when doing the work on someone else's car or machine what started as a quick repair could potentially cost you a lot of money. There is quite a lot on this forum site below.http://www.ukwelder.com/forum/index.php?showtopic=6629
