Hey, My chev lumina's hood latch pin recently broke off and i need to weld it back in place. I plan on using a standard MIG welder dto do this. What precautions should i take to completely avoid frying the onboard computer, or damaging the battery/ electrical system. And in your opinion is this a good idea?

I usually disconnect the battery and ground as close as possible to where you are welding.

I don't know of any muffler shops that unhook the battery cable to weld on exhaust. I don't unhook the battery cable and ground as close to the weld area as possible.

What bracketchevy said x 2. Unhook the battery and groung as close as possible to the weld. You always want to do this on computer controlled cars, but I do it on any car I weld on (if I remember) Why take a chance by not unhooking it when a battery is so easy to disconnect?
I used to work in a chassis shop that modified new truck frames and we had something called a Zapper that you hook to the battery. I know there's something to it or they wounldn't have been so anal about it. I guess after a couple of fried computer controlled transmissions they figured they better do something.
I know I've heard of guys frying out their ignition boxes by not unhooking the battery.

I know I've heard of guys frying out their ignition boxes by not unhooking the battery.

Mallory Unilite modules are especially sensitive. I took one out just trying to jumpstart the Firebird one day. After reading up on it, I replaced it, and disconnect the module itself before any welding. Some vehicles and equipment, it's a must to disconnect the batteries. I've seen a couple of trucks and generators have the ecm's fried by people welding on the equipment without disconnecting the batteries. That's one of the first checks when you get a complaint of a no-start on something nowadays, just look for evidence of welding. As far as passenger cars go, to me, it's just good practice to disconnect. I've had a couple of intermittent faults with the wife's Durango since they did some warranty rust repair on it a few months ago. Just glitches, but who knows why? Never did it before, and it's intermittent enough not to warrant looking into, as in once a month or two.

Think about this. You have (SWAG) 40 plus computer wires with associated grounds going to different sensors and controls running through out the vehicle. You unhook one battery cable and now think the computer is protect!?

A buddy has a welding shop and was welding the tailgate on a dump truck. The truck was a little rusty and had a bit of trouble getting a ground. Any how all the bulbs on the rear of the truck were burnt out after the weld job. The arc welders voltage was 40 volts, a little to high for the tailights!