Farm Equipment - welding question

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welding question

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Category: Allis Chalmers
Forum Name: Farm Equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=15245
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Topic: welding question

Posted By: Dale
Subject: welding question
Date Posted: 15 Jul 2010 at 6:44pm

I remember a good discussion on here on what to do and what not to do when arc welding on equipment that has batteries/alternator/electrical stuff. Now I can't find it. A friend says he has never heard about taking precautions when welding so you don't destroy otherwise working stuff. Can anyone give me the scoop on what damage you can do by just welding away without regard to disconnecting batteries etc.. I'm not trying to win an argument as much as saving needless repair bills and a bit of "face". Thanks

Replies:

Posted By: jminpa
Date Posted: 15 Jul 2010 at 7:26pm

If you don't disconnect the battery before you weld you can mess up the computer in a vehicle

Posted By: CTuckerNWIL
Date Posted: 15 Jul 2010 at 7:29pm

I didn't see that thread but would guess if you disconnect the ground cable from the tractor and make sure your welding ground is close to your work you wouldn't have any problems. you wouldn't want to ground to the drawbar then weld on a fender for instance, because of all the connecting points could arc and cause things not to pivot or swivel as they should.
I guess even with the ground disconnected you still have a potential ground through light bulbs and anything else with a connection to ground through some kind of resistance. If the points are closed the coil is grounded etc.
If I have to weld something on a tractor I take it off and bring it to the welder if possible.

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Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF

Posted By: Gerald J.
Date Posted: 15 Jul 2010 at 7:35pm

Two summers ago, I had the back bumper welded back on my camper with the trailer and umbilical connected to the truck. The next day I had the light on that says no alternator output and it took a new alternator get charging again. The ground was on the trailer close to the bumper mount.

Gerald J.

Posted By: CTuckerNWIL
Date Posted: 15 Jul 2010 at 7:40pm

That would bite, Gerald. It sounds like you would need to disconnect anything with a potential ground. That current must have found a wire going back to the alternator and made its own path to ground.

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Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF

Posted By: DREAM
Date Posted: 15 Jul 2010 at 8:25pm

It usually will Charlie. I would highly recommend disconnecting the battery before starting welding on ANY part of a vehicle or equipment. Another thing that was touched on already but maybe should be stressed a little more is moving parts, including engine reciprocating assembly. Arcing inside the engine is possible if welding on the block somewhere. Crank, rod, and cam bearings, as well as piston to cylinder or rings can be damaged by a stray current looking for a good path to ground, and you wouldn't even know it until the knocking started. Remember that electricity is looking for the BEST path to ground. If the one you make isn't the best, and it finds another path, it will take it. It may not be the shortest path, just the best one. Never put the ground anywhere there will be bearings, bushings, or other moving parts between it and the work area, and always grind or clean the ground area just as well as the area you will be welding on. A magnetic ground clamp works well for flatter areas, and lets you put the ground right next to the metal to be welded.

Posted By: island200
Date Posted: 15 Jul 2010 at 9:30pm

Last week I had to weld up a rear bumper/hitch back onto my grain truck. I did everything that was recommended in these posts except for disconnecting the batteries. Good news is that I can tow my grain auger with the grain truck again. Bad news is that I don't dare shut the truck off when I get to where I'm going. I'm in for rebuilding an alternator that I bet doesn't have 50 hours on the last rebuild.

Posted By: RickUP
Date Posted: 16 Jul 2010 at 4:16am

Just remember, the welding curent will take the shortest route. Example, If you are welding on the rear bumper of a vehicle, then clamp the ground on the rear bumper. The curent will not travel through the vehicle at all. If you accidently arc somewhere else on the vehicle, then it's anybodys guess where the curent might travel. Must be careful.

Posted By: DMiller
Date Posted: 16 Jul 2010 at 4:24am

The ground also has to be 'Clean', really good and shiny clean or the arc may transition anywhere through the chassis to get to ground, many times I will even weld the ground clamp to a frame to be assured it will maintain.

Posted By: Lance/SC
Date Posted: 16 Jul 2010 at 8:19am

I have one of the magnetic grounds that I got when I bought my mig welder but have never used it. I have never welded on anything on a vehicle but my son does on occasion but doesn't use one. Does the ground have to be clean of paint etc...if a magnetic ground is used?

Posted By: Rawleigh
Date Posted: 16 Jul 2010 at 1:43pm

Lance: Yes. The magnet just hold the ground up against the metal.

Posted By: Roddo
Date Posted: 16 Jul 2010 at 4:27pm

There is also a product out there called Anti-Zap. It goes on the battery and soaks up any electronic damaging voltage spikes. I use one at work all the time.

Posted By: Brian Jasper co. Ia
Date Posted: 16 Jul 2010 at 4:54pm

When attaching a ground for welding, I almost always clamp a large Vise Grip on the work piece close to the weld area and put the welder ground clamp on the Vise Grip. The shiney Vise Grip makes a better contact path than just on the work piece alone. I can see how a bad connection could find it's way through other things and let the smoke out.

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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford

Posted By: Clay
Date Posted: 17 Jul 2010 at 8:02am

Be sure to write down the radio station frequencies before you unhook your battery.

Posted By: Tom Miller (IA)
Date Posted: 17 Jul 2010 at 10:36am

I also use the anti zap on my welding jobs! I also use it when i do plasma cutting on equipment just for a little piece of mind.

Posted By: Amos
Date Posted: 17 Jul 2010 at 5:08pm

Using a surge/spike protector is the best/easiest way to prevent a electrical problem after welding on any vehicle/machine.

Unhooking just the ground cable off the battery is not sufficient as some on board electronic systems use only very small current amounts from the positive (I don't know how this works only was told it by an engineer that works on the engine control systems for a major automaker). He told me make sure you unhook both the positive and the negative. I was working for a neighbor with a brand new Volvo truck about 20 years ago that had the first 60 series Detroit diesel I ever saw in it. Cost him over $1000 for a new engine control module after making a set of ramps on the rear frame rails to get the float neck to ride up to the fifth wheel on.