"SteveB" toquerville@zionvistas writes:

My SIL is a good guy and treats my daughter good. He can't back a trailer
for crap, though. He put two nice dings in my truck so far, and I've had to
repair two trailers.

He comes to me with his Yukon Denali. It has a small 4" x 4" plate where
the plug plugs in that has somehow (?) been ripped off the bumper right
along the original MIG welds.

No problem, sez I. Sez he, "Aren't you going to disconnect the battery so
it doesn't foul up the computer?" I really don't think it's going to put
any electricity into the system, and it's not welding near any computer type
component, so I sez no. But, I tell him I'll check with the pros.

I've heard to disconnect the battery, and not to disconnect. When is it (is
it) appropriate to disconnect?

I've heard anecdotal stories from people claiming that somehow welding
on a vehicle without disconnecting the battery caused computer
problems. If somebody would come up with a plausible explanation for
how this is possible (even if only for a particular process, like
TIG), when the ignition system doesn't do it, I'd love to hear it.