A friend has an 2008ish Jeep Wrangler and he's wanting to do some welding to the frame. What precautions do we need to take to protect the electronics? Is disconnecting the battery enough? Keep the welders ground clamp as close as possible to the weld?
Just ground to what you're actually welding.
I never disconnect my battery or ECU. Not that it can hurt, but the charge will travel the shortest path to the ground, so just ground to the frame itself, assuming the battery ground is not attached along the path.
Definitely disconnect the battery. That ONE time I welded on the muffler on my Defender without disconnecting it and it blew out the ignition module on my distributor. And this was with the ground clamped to the same pipe about 9" from the weld.
-Hans
I've never disconnected the battery for welding on anything. Exhaust work, frame repair (I happened to put frame caps on both sides of a Wrangler a year or two ago, coincidentally enough), fabrication of mounts including the major suspension changeover my RX-7 has... nothin'. Never an issue.
Incidentally, found these in my camera dump folder, this thread got me arsed enough to upload them.
Meet Sawzall-surrogate:
By date stamp, I did this in July 2015. I remember it was berking hot and I was wearing a heavy coat to keep the rust off of my skin and I got severe chafeage from using the reciprocating saw for what felt like an hour with my arms well-lubricated with sweat.
That was "fun". Came in with a slipping clutch, and we noticed that, hey, the trans crossmember/skidplate was only held in by two bolts, we should probably fix that while we have the trans out. And by "slipping clutch" I mean you could shift it into any gear at a standstill without pushing the pedal and the car wouldn't even lug the engine down any.
Just ground close to your work and you'll be fine. Disconnect the battery if you like, won't hurt.
Whatever you do, make sure your ground path doesn't need to travel through a heim joint or shock 
Had a friend wreck a $400 coilover like this 
In reply to Knurled:
Wow that's a parts car down here.
Thanks everyone. I'll disconnect the battery to be safe but seems I was worried more than I needed to be.
In reply to Stampie:
"Parts car" up here is something that has a blown engine and floors you can see through AND is new enough that it isn't worth fixing. IIRC that Wrangler's total repair bill was in the $3k range, between the clutch and the frame repair and other things it got. The frame caps are readily available from a supplier whose name I can't remember right now. They were kind of a PITA because the crossmember bolted to them so you HAD to cut the bottom out of the old one. I've capped Toyota frame rust before with a lot less hassle. 3-4 hours labor and a measure of 16 gauge and a little paint, and it's good to go for another 2-3 years.
I actually saw this particular Jeep come back last week for servicing. Yep, I still don't like the way Wranglers drive, but at least the repair is holding up nicely...
IMO, a rust repair like that is worth doing if it's just one or 2 damaged areas and the rest of the vehicle is still in decent shape.
99 times out of a hundred, everything goes fine.
The basic advice about current seeking a ground is fine, for what it is. But, electricity will indeed do parallel circuits. So while most of it may well be going down the ground, some of it will be wandering off elsewhere. The fancy geek name for this is Kirchoff's Law.
Yes, keep the welder clamp nearby and on clean metal.
In reply to foxtrapper:
I have been known to clamp a bolt in the ground clamp, push the bolt into the thing I'm welding, and burn a bead from the bolt to the frame/part. Welding heat cleans the rust and you're left with a clean piece of metal to ground to. (If the bolt is welded on, by definition it has good contact!) It can be knocked off and ground flush again if desired.
You'll need to log in to post.
