Can you think of what else to unplug before welding?
 

DME, DME relay, wires to coil, three sensors.
How 'bout the plug(s) at the rear relay board?
Where is the speedo pick up?

Milt, our rule is anything that pertains to charging system and ignition. So Battery (at least the ground), alternator, coil, distributor, dme, etc.

OK, I didn't forget the battery here, just on my post.

Any way to disconnect the alt externally?

On second thought, I'm welding on the muffler. I think I'll remove the muffler instead.

...waiting for the PB Blaster to do its magic.

Anyway, this stuff is good to know. This ol' '88 is a lot more complicated electrically and electronically than my '71. :D

Milt,

Factory alarm module is famous for dying at the paint & body shop, and rendering the car un-startable!

Ouch. Glad I just removed the muffler instead. And, I found the hanger was broken, so I got a little extra repair in.

Gonna take a ride tomorrow!.

Thanks, Warren.

Yet another convincing argument to go with carburetors. :)

Not really. You still have the 14 pin connector, the dizzy (especially the tach lead on early cars), the battery, the CDI and maybe some more. All these cars are different.
But the later ones can get harmed easily, IMO

Wouldn't proper grounding take care of any non-computer issues?
I've been welding on my car for years with no problems.

I've done quite a bit of welding on my '85 and other than disconnecting my battery I've done nothing special. Never had a problem as a result. Luck perhaps?

I have welded on lots of cars - call me crazy - but never unplugged anything and never a problem. I just put the ground clamp directly on the part I was welding which was almost always something on the exhaust system. Some of those cars had some very sophisticated electronics.

I have taken my cars to exhaust shop many times. As BertBeagle said, they never unplug anything even when I requested to unplug the batery neg cable.

Well, I guess there are two sides to a story. But, if something goes wrong, or you touch something you shouldn't in the darkness of the helmet, then it could be a problem. Someone recently blew their CDI (actually an MSD unit) by just touching and grounding the battery cable at the starter.

It's always good to be extra careful isn't it.

Clamp the welding ground cable close to the weld area (to ground). Since electric welding is a form of resistance welding (the welding tip creating the air gap resistance), the closer the ground clamp to the weld area, the shorter the current path. That's why welding a muffler is pretty safe and welding close to an ECU isn't. It's still a good idea to disconnect the ground cable, just in case.

Sherwood