Ready Weld affects the computer?

Submitted: Friday, Apr 16, 2010 at 16:20
ThreadID: 77756 Views:2806 Replies:4 FollowUps:11
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Gday fourbies,

Was just reading some of past posts on portable welding and the ready weld unit seem good to have.

Just a question (probably a stupid one), would portable welding, like ready welder on the vehicle, say the chassis or something attached to the body have any damaging effect to the sensitive computer or electricial components?

Cheers

Nick
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Reply By: Fab72 - Friday, Apr 16, 2010 at 16:23

Friday, Apr 16, 2010 at 16:23
YES... that's why you should always disconnect the battery. Same goes for trailer/caravan repairs, if still hitched tothe car.
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Follow Up By: Fab72 - Friday, Apr 16, 2010 at 16:24

Friday, Apr 16, 2010 at 16:24
P.S. No such thing as a stupid question.
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Reply By: Member - Allan B (QLD) - Friday, Apr 16, 2010 at 17:41

Friday, Apr 16, 2010 at 17:41
Nick, by "computer" I presume you mean the engine management system and such not a laptop on the back seat. To which the answer could be .... maybe.

The absolute main consideration when welding on a vehicle, computerised or otherwise, is to ensure that the welder earth lead is attached firmly to the actual piece of metal that you intend to weld. Not to a convenient spot nearby.

The reason is that if there is not a good electrical continuity between the piece being welded and the piece where the return is connected then current may flow between them via an alternate route and that path may include components and wiring which probably will not take kindly to the current flowing through them.

Cheers
Allan

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Follow Up By: _gmd_pps - Saturday, Apr 17, 2010 at 14:48

Saturday, Apr 17, 2010 at 14:48
THIS IS THE ONLY (ALMOST) CORRECT ANSWER !!

You ALSO disconnect the battery minus from the chassis on ALL batteries.

And then you remove all the rust and paint from your clamp connection point
as close as suitable from the weld point to ensure THE BEST connection you can achieve. Because:

unlike popular opinion even when battery is disconnected you can have stray currents as mentioned around a longer route back to the weld point and that is potentially harmful because these are HIGH currents and even with DC welding you may get inductive spikes in board electronics because the flow across a chassis is NOT constant and can create EMFs where you don't want it.

When you ran HF/VHF/UHF radios you make sure your antennas have perfect ground. For most applications the power is low (5-20W) and RF interference
is much less like than with higher power.

When you run the legal 400W for ham radio in the car you want to earth your equipment as solid as possible as well as earth strips to the bonnet and all other parts with less than perfect earth to short the stray RF as good as you
can to avoid inductive damage or interference with others.

good luck
gmd
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Follow Up By: Member - Allan B (QLD) - Saturday, Apr 17, 2010 at 14:56

Saturday, Apr 17, 2010 at 14:56
Hey Oldtrack, you or me? Or would it be best to just ignore it?

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Allan

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Reply By: Nutta - Friday, Apr 16, 2010 at 19:49

Friday, Apr 16, 2010 at 19:49
Apparently migs are ok but with stick welders you have to remove the battery terminal.
To be on the safe side it wouldnt hurt to remove it either way though.

Wayne
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Follow Up By: Member - Allan B (QLD) - Friday, Apr 16, 2010 at 22:40

Friday, Apr 16, 2010 at 22:40
What's the difference between migs and sticks? Much the same current flows in the same places.

And just what does removing the battery terminal do? All the sensitive electronics are still connected to the wiring and body/chassis.

Cheers
Allan

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Follow Up By: Nutta - Friday, Apr 16, 2010 at 22:45

Friday, Apr 16, 2010 at 22:45
Come to think of it i think it was more to do with the alternator burning out diodes or something, which the stick would do.
I'm not sure what the diff is with sticks and migs on electronics.
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Follow Up By: Fab72 - Friday, Apr 16, 2010 at 23:06

Friday, Apr 16, 2010 at 23:06
Allan, removing the battery terminals ensures there is no completed circuit on the vehicle.

Electrical current needs a circuit to flow. Disconnecting the battery is like throwing a big "off" switch, essentially creating an open circuit.

Electricity will not flow into all the sensitive and not so sensitive electronics if there is no path for it to follow, in other words....a circuit.
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Follow Up By: Member - Allan B (QLD) - Saturday, Apr 17, 2010 at 09:19

Saturday, Apr 17, 2010 at 09:19
Yes Fab, I do understand about electrical currents needing a circuit to flow....... I am an electrical engineer.

But disconnecting the battery only creates an open-circuit in one part of the complex of circuits within the vehicle electrical system. There are still a number of "complete" circuits in which current could flow if introduced from an external source. This could be caused by inadvertent connection from an external source such ass a welder or even by induced RF energy. You would need to disconnect or open-circuit each and every such circuit to gain any immunity and maybe completely remove from the vehicle any electronic devices or components liable to be sensitive.

Disconnecting the battery certainly is "throwing a big off switch" for the battery but only for the battery which is unlikely to be affected by induced external energy. But, if it improves your feelings of security, by all means do it.

As I said before, the most important precaution to avoid problems is to ensure that the welding earth connection is attached directly to the piece of metal being welded and not to some convenient remote section of body or chassis.

Cheers
Allan

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Follow Up By: oldtrack123 - Saturday, Apr 17, 2010 at 11:58

Saturday, Apr 17, 2010 at 11:58
Hi

Alan said n'As I said before, the most important precaution to avoid problems is to ensure that the welding earth connection is attached directly to the piece of metal being welded and not to some convenient remote section of body or chassis.""

Yes & make sure that is the ONLY point & it is firmly clamped to bright cleaned metal.
AS a qualified electrician & a welding supervisor, I totally agree with with ALAN






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Follow Up By: Member - Allan B (QLD) - Saturday, Apr 17, 2010 at 14:05

Saturday, Apr 17, 2010 at 14:05
Oldtrack, it's really good to see that you and I have found common ground.

Cheers mate, Allan

Cheers
Allan

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Follow Up By: oldtrack123 - Saturday, Apr 17, 2010 at 14:16

Saturday, Apr 17, 2010 at 14:16
Hi Allan
Yes, but even on that thread that was locked You & I where in general agreement.
It was my use of the word "you"instead of 'one' ,in a follow up that you thought was aimed @ you [Alan ] that I think caused a problem.
Peter
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Reply By: tonysmc - Sunday, Apr 18, 2010 at 10:15

Sunday, Apr 18, 2010 at 10:15
I have done a fair bit of welding on vehicles and I use to always disconnect the battery. Then I was at an exhaust place and watched the guys welding mufflers, exhausts etc on the vehicles and then driving them straight away. I asked the question to them and the answer was "Never disconnected the battery and never had a problem" It wasn't just at one place but over the years I have noticed several do the same thing. Since then I don't bother.

Cheers Tony.
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Follow Up By: Member - Allan B (QLD) - Sunday, Apr 18, 2010 at 14:13

Sunday, Apr 18, 2010 at 14:13
Exactly!

Cheers
Allan

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