Somebody explain to me

David G · Apr 30, 2018

There was a lot of discussion here the other day about battery cables and welding.

My curiosity got the best of me, so I searched on the Internet and found a lot of opinions both ways.

So here goes. How does unhooking the battery help anything, when each component on the vehicle has a direct path to ground, then to the computer? I think it is just a wives tail, if you ground near the weld, and stay away from components and wiring harnesses, then it can have no effect. My personal thoughts is unhooking the battery would allow for more damage because it is a big capacitor.

Just the electrical/computer engineer in me thinking.

BobReeves · Apr 30, 2018

For whatever it's worth I agree with you.
Retired Motorola two-way radio tech

Doug - Iowa · Apr 30, 2018

I worried about that when I moved my welder rig from an old carbureted truck to a newer one with all the computerized engine controls. The chassis of the welder is bonded to the frame and I often weld on the tailgate as a bench. In the winter the truck is running while I'm welding to keep the cab warm, same with the A/C to keep it cool in the summer. Three years now and no issues at all. I'm sure if somehow part of the wiring harness got in series with the welding current bad things would happen but otherwise I'm convinced it doesn't matter.

Steve@Advance · Apr 30, 2018

I think it's wives tale too. I've never disconnected the battery, and never had a problem.

I think it would be possible to damage electronics under some conditions, like grounding the body and welding the frame, or grounding the frame and welding the exhaust system. Either way would send welding current through the chassis ground, which could send some weird feedback through sensitive components, maybe... Under that condition "possibly" the battery could serve as a conductor, but I'm still not sure.

Here's another thought... If it is possible to damage electronics with a welder, what about electrical storms? What about electromagnetic fields, as in driving under high power lines? Or driving through a tunnel with high voltage lines?

There has to be some safeguard against such sensitive failure. Think of the liability if computer controlled throttle suddenly lost it's mind!

mtny · Apr 30, 2018

Years ago my neighbor who was an equipment dealer told me the same thing , never weld on vehicles with cables hooked up . As stated its all grounded anyways . I"ve done it n numerous times since.

ed will · Apr 30, 2018

Hi, I think I would just disconnect the battery cables if I had some doubt. Not a big deal for piece of mind. Ed Will Oliver BC

451 CUBES · Apr 30, 2018

I was always taught to disconnect the alternator, right or wrong. This was back before electronics, excepting maybe a radio. The only situation I could ever see damaging the alternator (or any electrical / electronic components) would be if one accidently applies voltage from the welder to a vehicle circuit i.e. burning through a harness etc.

On another note, never allow a bearing to be in the ground path of a welding setup...no wives tale there.

guido · Apr 30, 2018

Hello David G,

I agree, old wife's tale. Cables on and nothing is energized? What's the problem! Have always had a good ground, not the spring type. Close to the welding area, never seen any smoke out of the electronically controlled diesel engine we had at work.

Guido.

bradley martin · Apr 30, 2018

Lightning strikes can fry the electronics on modern equipment. A neighbor with a relatively new John Deere tractor was baling straw last summer when a thunderstorm came up. He left the tractor in the field, and went home in his pickup. Later that day, he drove by the field and noticed the lights on the tractor were on. He went to investigate, found he couldn't get the lights to shut off or the tractor to start. Dealer came out and they couldn't either. Tractor had to winched onto float trailer and taken to town. I was told that the bill was over $10,000. To repair damaged electrical components.

Brendon-KS · Apr 30, 2018

There is very structured testing that occurs during product development to safeguard against exactly what you're talking about. The test consists of bombarding the wiring with a wide spectrum of frequencies and watching the controller outputs with an oscilloscope for any sign of weird behavior. The test is quite severe in that the emitter is literally clamped around the wiring harness so it is a lot stronger of a signal than what would reasonably be experienced during normal machine operation. A second part of the testing is to make sure that the machine itself isn't emitting electro-magnetic interference (EMI) that could cause problems for other devices. This is a lengthy test and usually takes several full days to complete depending on the complexity of the machine's electronic systems. Ideally the testing would happen in a specialized "clean room" that is shielded from external EMI but due to the physical size of some machines it is also done in shop buildings that are free of "electrically noisy" equipment like welders and two-way radio systems. Most companies would regard passing these tests is a prerequisite to serial production of machines with critical electronic controls.

504 · Apr 30, 2018

The one thing overlooked is the computer is the ground switch on a lot of automotive systems. The power is always on.

guido · Apr 30, 2018

Hello Bradley Martin,

30.000 Amps will fry a few things in its path, that is the average bolt of negative lightning. They do strike much higher then that! Nowhere to hide, close enough and.....all is toast!

Guido.

fixerupper · Apr 30, 2018

I have seen welder damage to electronics once but it wasn’t from welding. A young man on the harvest crew tried charging a pickup battery with the portable welder. When he hooked it up he didn’t check to see where the welder was set and it was set at the highest amperage. He hooked it up and walked away. Not very long later someone yelled “the battery is smoking”! After everyone calmed down the pickup was started but not did not run well. If I remember right the throttle body was overfueling. We had to onhook the battery to reset the computer every day until we could get it to a Chevy dealer to have the ECM replaced.

from the hill · Apr 30, 2018

Leave the battery connected, it's basically a short circuit with a 12 volt drop.

Ultradog MN · Apr 30, 2018

I think if the tractor is sitting on concrete you will have problems.
If you park the tractor on a couple of boards there shouldnt be a problem welding on it.
Wink...

Oliver 500 Wa · Apr 30, 2018

I've kicked this one around too....

When your DC stick welder is set to straight polarity or you are running flux core wire in your wire feeder welder, the "ground" clamp is actually the positive lead and the electrode or wire is negative. Seems like there might be a problem there but it's been done lots of times and never heard of any trouble

If you are using your DC welder with reverse polarity or running solid wire with gas in your wire welder then the ground clamp is negative and the electrode or wire is positive. Seems like less potential for problems there. This is what I've always done and never had a problem.

Throw TIG in the mix and my head really spins about what it might do. I've never TIG welded anything while still attached to the vehicle.....

3000OH · May 1, 2018

I think I can see one possibility, through a ground loop. Often see systems with multiple major ground points, in multiple places. There's more than 0 volts potential between those ground points even on a factory fresh setup, and only gets worse as rust & other corrosion gets in the way. From what I've understood, the systems are generally designed & tested to be tolerant of these somewhat floating ground levels (another post below talks about the testing). Under admittedly rare conditions I could see an unpowered but still-grounded device being caught in the welding loop path and seeing voltage potentials beyond 12-14V, and/or in a reverse voltage configuration. This also fits with the rule of thumb that, if you have to weld on a newer vehicle, keep a good welding ground point as close as possible to weld point - it would help keep the welding loop as small as possible. Like others, have never had a problem but the cost of diagnosing and replacing the black boxes keeps the pucker factor there.

1948CaseVAI · May 1, 2018

(quoted from post at 18:52:28 04/30/18) There was a lot of discussion here the other day about battery cables and welding.

My curiosity got the best of me, so I searched on the Internet and found a lot of opinions both ways.

So here goes. How does unhooking the battery help anything, when each component on the vehicle has a direct path to ground, then to the computer? I think it is just a wives tail, if you ground near the weld, and stay away from components and wiring harnesses, then it can have no effect. My personal thoughts is unhooking the battery would allow for more damage because it is a big capacitor.

Just the electrical/computer engineer in me thinking.

You are exactly right but those who disagree are dug in so deep it isn't really worth the discussion anymore. Many just do not understand so they fear most everything.

jacksun65 · May 1, 2018

I think That you are mostly correct, If you have a good ground if you are not close to a computer or other sensitive electronics If you don't run your cables next to any electronics. This is just the welder in me and military aircraft mechanic, But while working in a factory welding and grinding in the same area. I noticed while using a miller mig welder that everytime I was welding the grind dust on the floor would move toward the welding cables on the floor and create a pattern around them. I then realized that they were creating E.M.P. everytime I struck and arc. That's a Problem with todays electronics, they are not hardened against that.

dr sportster · May 1, 2018

Those who disagree seemed to have experienced some component failures due to welding. Those who got away without frying anything may have been lucky.

26cows · May 1, 2018

Info form a GM service manual about welding. Disable SIR system (air bags). Disconnect neg battery cable. Apply weld thru primmer to all surfaces. I have all ways heard it is best to disconnect the battery.

Somebody explain to me

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