# Welding?



## Detourer (May 9, 2005)

I need to do a bit of welding to the Chassis of the Unimog.....Whilst I can stick bits of metal together without too many blobs I can't remember......do I need to disconnect anything electrical/electronic on the vehicle?

..


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## bigfoot (May 16, 2005)

It would be advisable,esp electronic items.


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## aultymer (Jun 20, 2006)

On steel or aluminium boats we were advised to always disconnect the batteries before doing any welding on the hulls. 

No doubt someone will be able to advise on electronics with built in power sources.


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## Chausson (Oct 17, 2006)

We always disconnected the battery, it only takes a minute better safe than sorry.

Ron


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## hilldweller (Mar 8, 2008)

Detourer said:


> ..do I need to disconnect anything electrical/electronic on the vehicle?
> ..


Better safe than sorry.

Just how close to anything electronic are you ? How close to any cables ?


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## Detourer (May 9, 2005)

Not close to cables or anything like that.........It's just an external bracket to carry a mountain bike......just in case someone ever feels the need :wink: .............

Its on our "Support" truck so loads of batteries i.e. two big jobs for the engine and 4 very nearly big leisure things. All well tucked away.

I guessed [and thanks you all for advice and conformation] disconnect bats but it is over 100deg down here in Spain at the moment and even hotter inside vehicle........Night job I think........ 

..


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## mangothemadmonk (Aug 6, 2006)

The only reason you would disconnect the battery is to stop delicate electronics blowing.

You can get a spike protector which fits on you battery like one of

These

You can get cheaper.

Johnny F


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## AberdeenAngus (Jul 26, 2008)

Disconnect the ground strap (-ve) on your battery.
Make sure the ground clamp for your welding set is as close to the weld point as possible.


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## OldWomble (Jul 6, 2008)

AberdeenAngus said:


> Disconnect the ground strap (-ve) on your battery.
> Make sure the ground clamp for your welding set is as close to the weld point as possible.


Yes agreed - the closer the better!


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## aultymer (Jun 20, 2006)

I was hoping someone with a bit of electrickery know-how would come along and explain why most of us do disconnect before welding. 
What is the reasoning behind this? I realise that a high voltage can exist especially when striking an arc but don't know if this generates a spike in another circuit. 
As said before, better safe than sorry but has anyone done any damage when welding? (apart from the obvious, setting fire to bits inside or burning pipework)


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## hilldweller (Mar 8, 2008)

aultymer said:


> I was hoping someone with a bit of electrickery know-how would come along and explain why most of us do disconnect before welding.


I can't work that out, if you mean battery, with battery disconnected you have a pair of substantial aerials, with battery connected you have a big load on those aerials.

What is at risk is the delicate stuff like GPS with external aerial, like the long wire back to front for a camera. And the most frightening of all the vehicles engine computer and anti-lock brakes, you'd not want to fry those and also very difficult to disconnect.

Bolts cause few problems.


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## AberdeenAngus (Jul 26, 2008)

If you want to know what can happen watch what happened to the ABS on Claudio's bike on "Long Way Round".


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## mangothemadmonk (Aug 6, 2006)

That's why I suggested an ELECTRONICS PROTECTION DEVICE.

Johnny F


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## aultymer (Jun 20, 2006)

> And the most frightening of all the vehicles engine computer and anti-lock brakes, you'd not want to fry those and also very difficult to disconnect.


This exactly what I wanted to know, for my own information and Detourer.

How do you protect modern imbedded computer systems?
My old Land Rover needed 1/2 a days welding for the MOT every year but all we did was remove the neg connection on the battery and all was fine. 
What do you do with electronics which cannot be disconnected from the chassis and contain volatile memory or rechargeable power supplies?
Will Mangos EPD protect all these?


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## bigfrank3 (Mar 26, 2007)

The reason the battery should be disconnected is to take the alternator out of circuit. This has electronic components inside usually diodes. These pass electricity in one direction only. If the voltage is too high as it will be in the case of welding voltage it will breakdown the diode barrier and so cause an expensive repair to the alternator.

I am assuming that you are using a MMA (manual metal arc) welding machine, a so called stick set. The open circuit voltage on these are usually between 50 and 80 volts AC. 

With the battery disconnected all electronic equipment will be safe.

Another type of welding is MIG welding when a wire is fed down a torch to act as filler metal the open circuit voltage will vary between 15 and 45 volts DC. 

A third type of welding is TIG. (Tungsten inert gas) This is where an arc is struck using a tungsten electrode and a filler metal is manually used. The arc is usually created initially by using a high frequency and can have a voltage approaching 18.000 volts. This will usually fry associated vehicle electronics unless they have been disconnected. 

If in doubt disconnect the battery.

I know next to nothing about vehicle electrical systems but I have been repairing welding machines in all there shapes and sizes for the last 33 years. Good luck with the welding and don't forget to cover everything to avoid splatter. Frank


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## hilldweller (Mar 8, 2008)

aultymer said:


> > How do you protect modern imbedded computer systems?
> 
> 
> Don't weld. Because you can't protest the system. You can minimise the risk by keeping the welding circuit as short as possible - as someone else has already said.
> ...


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