"Joe Pfeiffer" wrote in message
...
"Leo Lichtman" writes:

"Curt Welch" wrote: (clip) It seems to me that keeping the battery
connected is more likely to protect
all the electronics in the car than harm them while welding. It acts as
a
voltage regulator so in case there are any currents induced in any of
the
wires, it's more likely to clamp the voltage levels to 12V instead of
allowing them to rise to higher levels that could do some harm.
Actually, following that logic, you should turn everything on--radio,
ignition, lights, global navigator, etc. Otherwise, the 12v clamp isn't
there.


Just about anything somebody would regard as "modern" electronics that
might be damaged by the welder is actually still powered-up (albeit in
a standby mode) even when the ignition is turned off -- that certainly
includes the engine controller and radio. Haven't checked, but I'd be
pretty surprised if that wasn't also true of the transmission
controller, GPS, etc etc.

The only thing I would expect to be protected by disconnecting the
battery
is the battery.

And it will carry more current without harm than most welders will put
out.

Right.

I wouldn't worry too much about the battery for the reasons stated above.
The point of disconnecting the battery is to protect the electronics. Most
electronics are not designed for reverse polarity. The possibility exists
when welding for forcing current back through the "wrong" side of the
battery - not normally a problem as that's how battery chargers work. The
issue is the potential for allowing the current through the electronics
first.

We could argue for ever about it and only the auto electronics designer
knows for sure. Given the cost of replacing the electronics it seems like
cheap insurance to break the electrical path through the electronics (i.e.
remove the battery cable). I think that everyone would agree that if the
conductive path through the electronics is removed then the likelihood of
damage is significantly reduced.
hope this helps