Disconnect negative terminal before Welding.

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Ok, so I also post on a tractor forum as I live on a small ranch in Texas. The question came up on the tractor forum about should one disconnect the negative battery terminal on a truck, tractor (farm), etc before welding on the vehicle.So I thought I would bring this question over here for expert advise from the knowlegable contributors here.Sign on East Texas payphone: Calls to God 40 cents......it's a local call...
Reply:Stamp,I think we just had a thread on this, but its always nice to be able to help someone...Here's my take...I have welded on many tractors and pieces of equipment, cars, trucks etc. and have only once or twice disconnected the cable.  The only ones I did were ones with more modern computers.  But, by and large, unless you have the cable ground clamped to the alternator bracket, you should be fine.   The idea is to try not to pass the current throught the alternator or any circuit directly connected...Electricity will take the path of least resistence.  There are finer electronics on modern CARS that could be affected, but then, any welding could affect that depending on if it was HF or not regardless of whether they are "grounded" or not, because they store things magnetically.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:I've always been told to keep your ground clamp close to your welding and you will be ok.
Reply:You should ground as close to the work like Brianstick said. But the is another reason you would want to disconnect the negative, if it is a negative ground. You may burn up some insulation somewhere if you are welding close to some wires. When you disconnect a battery, you should always disconnect the negative side first. If your wrench hits the frame while you are disconnecting it, nothing will happen. Once the negative side is disconnected if you hit the frame on the positive side, nothing will happen.You would be surprised how many of the people changing batteries at the Auto Parts stores don't know this.  It is " Ungood" if you first disconnect the positive side and hit the frame with the wrench.
Reply:There are people who work in auto part stores that don't know the difference between a push rod and a connecting rod! They are behind the counter because they have good computer skills and know how to fetch parts.
Reply:I'm an auto technician and have a good deal of training from Toyota. They recommend disconnecting the ECM from the harness before welding. Disconnecting the battery may protect the battery but if the other components are still connected to the chassis there is a chance (however small) that one could fry some expensive components.Now from my personal experience, I am not aware of any instance where welding has caused a problem with electronics. And It's beyond me that if you ground to the part you are welding on, how current could stray outside of that loop.Don't talk about it, Just do it!
Reply:we ha had e guy smoke two computers on a excavator wile welding on brackets for a clamp for hydraulic hoses
Reply:This is one of those precautionary deals that most people have heard about. I kind of look at it this way, it won't hurt to disconnect a battery ground or connection to a black box. Is it really needed? Well maybe, maybe not, likely most times you will be alright, specially if you put your ground clamp close to the work. But you never know sometimes stray currents have a mind of there own.  If it were my own vehical I would likely be to lazy to do it, If I was working on someone elses I probaly would.Last edited by dakook; 02-21-2009 at 05:21 PM.
Reply:Originally Posted by thebighammer1we ha had e guy smoke two computers on a excavator wile welding on brackets for a clamp for hydraulic hoses
Reply:Guys put pits on bearings and cook stuff all the time on equipment.
Reply:sandy  he was welding on the arm neer the bucket link  it only takes a few millie amps to fry a micro prosseser they can be fried out with a test light form back feed his clamp was on the welded bracket ware aux hydralic pipe goes on