welding on c4
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 763
Likes: 0
From: pa
i am going to disconect both pos and neg. when i dont know.... i err on the side of overkill. i hate haveing to fix a screw up, so i can get back to fixeing original problem........thanks for input.
Burning Brakes
Joined: Dec 2003
Posts: 1,183
Likes: 1
From: MidOhio
The problem with welding and electronics is hi voltage spikes getting imposed across any of the low voltage electronic components. These spikes can be gererated by induction from the welding cables being near any other wire conductor or other electrical conductors, i.e. steel and alum. The welding voltage itself is fairly low. I'd suggest you leave the battery connected, ignition off and keep the welding leads as far from the car as possible. The common practice in muffler shops of the car on a lift and weld cables dropping straight down to the floor then over to the welder (position the welder power supply so the cables get out from under the car as directly as possible) is as ideal as you can get-probably why they have very little trouble with fried electronics. Keep the positive and negative cables together as much as possible up to the site of the weld (the electric/magnetic fields they generate help cancel each other) and attach the ground clamp as close as possible to the weld area. Isolating the electronics by disconnecting the battery can leave the electronics able to build a high voltage charge because there's no circuit for the excess voltage to drain off. You should be ok. 
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
The reason why you disconnect the negative cable on your battery when welding is because the welding current through the frame places the welder voltage across the frame in series with the battery and electrical loads then become supplied with 12v in series with approx 25 vac from the welder and most car electronics cannot tolerate that.
Race Director
Joined: Nov 2006
Posts: 13,269
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From: Sunshine Coast, Queensland, Australia
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I've done a lot of welding on motorcycles. Once I fry ed the ECM on a Harley. I've learned to unhook the battery, Unplug the ECM or Ign. module and keep the ground clamp for the welder as close to the weld as possible.
4th Gear
Joined: Dec 2006
Posts: 4
Likes: 0
From: las vegas nevada
learn from my experience disconnect the battery I cause all kinds of weird problems by not having the battery disconnected when i had my mufflers welded on. had to replace bat & atl and a fuse just my 2 cents
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If you have to weld on the muffler itself, just remove the muffler.
