Quote Originally Posted by fdcmiami View Post
all i can say is everyday, from one corner of the country to the other welding is being done on the backs of trucks. how many field fabricators disconnect their batteries to weld something. searching the net for instances of damage done from welding is like trying to find that mythical welder who had the cigarett lighter explode in his shirt pocket.

anyway, since it is considered a fact by so many you will be doing yourself a favor by just having the owner disconnect them otherwise if there is so much as a flat after you are done, it will come back at you. i did some repair work on two rolloffs yesterday; the owner said he was going to disconnect the batteries. do you think i argued the point? not hardly.
Properly designed electronics should have no problem, but there is the risk that they are not properly designed. My own stuff, I weld on all the time, occasionally with them running, even. Considering that some ECM's die for no apparent reason, in some ways it makes sense to reduce the risk. Having said that, just disconnecting and reconnecting the power is something that can take out a weak component. Of course the costumer will point the finger at you, no matter what. There are no guaranties in life.

I have had an MSD on a race car go bad from welding, but that was a high frequency issue, and a very old and abused MSD.

Quote Originally Posted by Trip59 View Post
Oddly, we noticed it not too long after we were talking about the sticker on the frame warning not to weld or drill the frame as it was heat treated.
Many years ago I wish I had taken a picture of a semi frame that had such a warning stamped right into the aluminum frame. It had been converted from a tractor to a dump truck, and there was a beautiful weld bead right through that notice, where the frame had been extended.