Welding items attached to vehicles

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I want to build a flatbed and a new bumper for my truck. I've built/welded quite a few racks and other truck accessories, but I've never built them while they were attached to the truck.What kind of precautions do I need to take before hooking my mig welder up to steel attached to the vehicles frame? Disconnect the batteries?Thanks-Chris
Reply:just keep your work (ground)clamp close to the weld area so that current is not flowing thru bearings or electronics.miller thunderbolt 250vlincoln square wave tig 175 prolincoln idealarc mig sp250everlast tig 210EXTeverlast power plasma 50chicago electric (hf) 130 tig/90 arcchicago electric 90 amp flux wire3 sets oxy/acet
Reply:Don't know if it makes a difference, but I always disconnect the ground cable from the batt to protect electronics. I figure better safe than a bunch of $$ out of the wallet.                                             MikeOl' Stonebreaker  "Experience is the name everyone gives to their mistakes"Hobart G-213 portableMiller 175 migMiller thunderbolt ac/dc stick Victor O/A setupMakita chop saw
Reply:I worked for a trailer mfg. back in the day and we always disconnected the batteries when installing a flatbed. Better safe than sorry!Its not a bad idea to cover gas and break lines in the work area also.Thermal Arc 210 FabricatorHypertherm PM 45and lots of other tools the wife doesn't know about
Reply:This might answer one of my questions too - you mount a vise on flatbed - do you unhook truck battery before you use it? - i don't think soThe main thing is not to panic or get excited Bobcat 250, X-Treme 12VS,  MM211Meltabo, Milwaukee,Porter Cable,Dewalt,MakitaVictor O/A, Ingersoll-RandEvolution Rage2, 40 amp PlasmaLincoln 225 AC/DC
Reply:Don't disconnect the batteries, I weld every day off the back of my truck and haven't fried a single thing
Reply:Originally Posted by riflecoDon't disconnect the batteries, I weld every day off the back of my truck and haven't fried a single thing
Reply:I would disconnect the battery or batteries. Doing this isolates the vehicle electrical system from the frame. All heavy truck and equipment companies tell you this is a must do before welding repairs. I have personally replaced the complete harness pluss all the eletronic controls on an ex 450 hitachi. This was all damaged by someone doing welding repairs. It only takes a few minutes to diconnect the batts. Also you should keep your ground as close to your weld as possible.
Reply:Also I should add that welding off the back of your truck is a different situation unless you have your work lead clamped to the frame of the truck. I have welded off the back of my truck and the work lead is always attached to the piece I am welding.
Reply:i weld off the back of my rig all the time. and i dont have the ground hooked directly to the piece im working on. ive got 2 grounds coming from my machine. one bolts directly to the bed, and the other goes to my lead reels. that way if i hav to come back to rig to work off of, i only have to drag + lead. ive never had a problem with wiring, electronics, etc. kwMM 251MM 135Lincoln Pro cut 55Bobcat 250Miller Thunderbolt ac/dcolder ac forneyJackson nexgen 3n13-Smith OP setups97 Dodge dieselMakita chopsawJet swivel head bandsawlincoln tig 300/30030a spoolgunpuma port. gas air comp.
Reply:Common sense, keep your ground close to your repair.  Electricity not only takes the easiest path to ground, it takes others as well (watch lightning).  Mfg's will tell you to disconnect batteries, although I never have.  I assume you could be liable if you don't. I know OTC and other Mfg's make surge protectors that just connect to the batt for welding protection.  I have know idea how they work, in my logic they wouldn't if current was travelling through an ECM or bearings.  Does anyone have experience with them?
Reply:1: Make sure the current can not take another route through the wiring. This may fry those wires, or the magnetic field around the wire carrying the current may induce a high enough voltage in paralell wires to fry electronics (magnetic field around one wire inducing voltage in another is a basic transformer!).2: Make sure the current doesn't pass anywhere near the wires on the vehicle. Again, high welding currents create a fluctuating magnetic field, and any metal inside it will convert some of that back into electricity. Most people never have any problems with frying electronics in cars, but find out what the electronics in your car costs before you decide if it's worth to gamble. To protect, say, the main computer, you really have to pull the plugs out of it. Disconnecting just a battery will not stop the wires running all around the car from picking up a high voltage pulse from welding and carry that to the computer, or any other type of sensitive electronics...
Reply:I agree, I see no sense in the commercial surge protectors, although I don't know the theory behind them.  I am very caefeful where my ground is though. Arc electricity will travel wierd places, and if it goes through bearings or ECM's, it will create all kinds of problems. Remember there can be more than a dozen ECM type components on newer vehicles, including on the main frame.  GMC ABS ECM's were mounted on the truck frame for years if my memory serves me right.