Welding & Why

[ova50]

Over the years I have heard a number of claims or opinions about welding on vehicles, in particular with the use of stick & mig welders or any electric type welder.

Some say to disconnect the battery. Some say doesn’t matter.
Some say disconnect the ECU. Some say doesn’t matter.
Some say disconnect both, and so on.

Things I have been told are batteries could explode, over heat, and be damaged. {I realise that welding or creating a spark near a wet cell battery can cause a bang}
Or the vehicles computer unit can be damaged.
When I have asked for more details about this no one has been able to supply any first hand experience of problems, only what they have been told or heard.

Has anyone had any bad experiences with not disconnecting before welding.
I’m not planning any welding on the vehicle, but would be interested to know.
Thanks

[mick.]

Yes I've seen a computer fried in a panelshop from a panel beater. One of the other panel beaters decided he wanted to borrow the anti-zappers that was on another car while the other panelbeater was putting one of his other jobs back together. When he come back he started tacking up his quarter panel. Once the job was finished he noticed his anti zappers wheren't on but at the time didn't think anything of it. We went to move it to the paint shop and the car wouldn't go. After stuffing around for a while called out the local auto electrican down and he worked out it was a fried computer. It was a Lexus LS460 so the computer was over $5000 to replace.

So yes it can stuff your computer pretty easy. The thing is you could weld up 100 cars and not have this happen but then one day you do. So it's not common but when you weld cars all the time anti-zappers are very cheap insurance.

Basically what causes it is the high voltage that can go though the car when welding but I remember an old panel beater telling me that the main cause is a bad earth when welding can cause a sharp jolt though the body of the car causing it to fry anything electrical.

Cheers Mick.

[Steve4wdin]

It is the same principle with jump starting cars. Never put earth to earth as it can do the same thing. As Mick said, not common but expensive

[threedogs]

Most newer style jump leads have the anti zap box on them............ Will put pic soon

[Ben-e-boy]

Over the years I have heard a number of claims or opinions about welding on vehicles, in particular with the use of stick & mig welders or any electric type welder.

Some say to disconnect the battery. Some say doesn’t matter.
Some say disconnect the ECU. Some say doesn’t matter.
Some say disconnect both, and so on.

Things I have been told are batteries could explode, over heat, and be damaged. {I realise that welding or creating a spark near a wet cell battery can cause a bang}
Or the vehicles computer unit can be damaged.
When I have asked for more details about this no one has been able to supply any first hand experience of problems, only what they have been told or heard.

Has anyone had any bad experiences with not disconnecting before welding.
I’m not planning any welding on the vehicle, but would be interested to know.
Thanks

It is good practice to remove the battery earth.
You can get away without doing this IF you have a good earth to the welder and that earth clamp is as close to the job as possible. Current always follows the path of least resistance. If you have a bad earth on the welder, or for some reason have the earth lead a long way away from the weld. The current from the welder will want to, as stated. Travel the path of least resistance to earth, which could easily be the battery, ECU etc

[ova50]

It is good practice to remove the battery earth.
You can get away without doing this IF you have a good earth to the welder and that earth clamp is as close to the job as possible. Current always follows the path of least resistance. If you have a bad earth on the welder, or for some reason have the earth lead a long way away from the weld. The current from the welder will want to, as stated. Travel the path of least resistance to earth, which could easily be the battery, ECU etc

If the battery was disconnected or even removed, is it possible that the ecu could still be damaged by welding.

As I said, Im not planning a welding job but if I ever needed a welding job done I would want to know that who ever was doing it had taken steps to avoid frying something.

Thanks

[Alitis007]

As long as the battery is disconnect the surge in power from the arc will travel its easiest path being straight to the electrode. The battery in a car completes the circuit so as long as the terminals arnt connected there won't be any dramas. I have seen batteries explode from welding and computers as well but NEVER had any dramas when the battery is disconnected!

[ova50]

Thanks guys for clearing that up for me.

Something I will remember

Regards