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View Full Version : welding to vehicles - any special rules?


nakman
04-07-2012, 11:31 PM
when arc welding to a motor vehicle, are there any special precautions that should be taken? Like, should the battery(ies) be disconnected? Anything else?

:weld:

kurtnkegger
04-08-2012, 07:49 AM
Any time I weld on mine, I A) disconnect the battery, and B) have a fire extenguisher at the ready. Look for spots below where splatter might land and possibly ignite.

thefatkid
04-08-2012, 08:26 AM
I unplug the expensive computers; engine, abs, aftermarket radio equipment. I'll also disconnect the battery. Anything close to the weld spot that is rubber I will lay a wet rag over. I also have a large fire-blanket for larger coverage (don't lay it on paint without a cloth under it though :rolleyes:)

Air Randy
04-08-2012, 08:51 AM
If you are welding to the frame, make sure you know whats on the other side i.e. fuel lines, wiring harness, etc.

AxleIke
04-08-2012, 12:21 PM
Second all of the above. Although I have never had a stereo worth worrying about, but the ECU gets unplugged, and battery disconnected.

And DOUBLE check the other side, as Randy say's.

Only other advice that I have is that, almost always (though not 100% of the time) electricity will take the shortest path. So, to eliminate issues with electronics in the vehicle, place your grounding clamp as close to your weld area as possible. This will reduce your risk of burning out any unplugged electronics.

rover67
04-08-2012, 01:16 PM
in addition to the above, make sure there are no rotating parts or any joints between the ground and where you are doing your work. Like worst possible thing to do would be to say ground a lug nut to weld a frame.

Then you'd probably hose everything in between, like wheel bearings, when they all arc while you start the weld.

just ground to the part you are working on.

nakman
04-08-2012, 10:38 PM
Good stuff, thanks! Maybe I'll stick to trailers for a while longer... much less prep! :weld:


edit: p.s. Randy, I'm getting better at your old welder, my last couple projects actually don't look half bad. I'm worse when I try to stick thin stuff to thick stuff, but when I can join two 3/16" pieces it's pretty sweet.. definitely having fun with this, my favorite sticks are the 6013's.

So far the camper has a new motorcycle carrier and upgraded battery holder, the utility trailer has a new battery holder, upgraded wheel pivot, and some new tie-down spots, my boy's motorcycle got a cut & turn on the handlebars to give him a little more reaching room, and my neighbors ATV plow got fixed this past winter. I think I'm most proud of the ATV plow. Not a bad winter of welding. :)

Beater
04-09-2012, 07:56 AM
welding blankets are not cheap, but indispensable

Air Randy
04-09-2012, 08:48 AM
6013 is anice all around welding rod, easy to use for just about anything. You can get it in different rod sizes too. If you get the smaller diameter stuff it will make welding the thinner material easier.

You're on the slippery slope for sure, next on your list will be a mig unit :D

Red_Chili
04-09-2012, 10:20 AM
I've welded repeatedly to the Chili and others with no concern for the ECM. I would NOT disconnect the battery... it acts as a clamping device. Think, capacitor. Shunts spikes to some degree. We are dealing with low voltages, but much current/ inductance. Operate accordingly.

Ground very close to your work and make sure you know what is near the welding location. Do NOT drape welding cables over anything, induction is real.

YMMV.

DaveInDenver
04-09-2012, 10:50 AM
Current follows the least resistance, but the forcing potentially is distributed. So grounding near the weld will reduce current elsewhere but the voltage is mostly uniformly present everywhere on the circuit. The battery is a shunt, but only to current near by and only to fairly low frequency currents. They are generally fairly high impedance to anything over a few KHz.

So the battery will likely be the next lowest path if you're grounded by the weld, but if the sensitive electronics are between the weld and the battery, the stray currents will flow past and some are bound to find their path home across the ECU or whatever.

The ECU will have shunts to protect against EMI/ESD. What happens is those guys are doing their job but repeatedly subjecting them to transients will eventually ruin them. The amount of energy is really very low, but the TVS diodes aren't designed for sustained surges. This is why the starter crank position turns off electronics, which would normally be tough on the shunts.

I'd physically disconnect the ECU and any important devices, although I would leave the battery in the circuit. It can tolerate anything a welder will throw at it and will, like Bill says, act like a filter.

Red_Chili
04-09-2012, 11:28 AM
BJ Goodheart came over to do some welding on Saturday, and had a suppression device designed for shunting transients when welding to vehicles. Looked intriguing. Easy too.

Rezarf
04-09-2012, 11:36 AM
All this and no one has asked "Nak, whatcha' welding man?" I am interested in what you are up to? :D

Red_Chili
04-09-2012, 11:36 AM
The ECU will have shunts to protect against EMI/ESD. What happens is those guys are doing their job but repeatedly subjecting them to transients will eventually ruin them. The amount of energy is really very low, but the TVS diodes aren't designed for sustained surges. This is why the starter crank position turns off electronics, which would normally be tough on the shunts.

I'd physically disconnect the ECU and any important devices, although I would leave the battery in the circuit. It can tolerate anything a welder will throw at it and will, like Bill says, act like a filter.
Um, the starter crank position doesn't take the ECM out of physical connection, does it? I thought the starter crank position turning off electronics was mostly to conserve current capacity... ?? And maybe keep voltage fluctuation damage from happening to that nice stereo due to draw down while cranking?

Taking the ECM out of physical connection would make welding to one's own vehicle a bit difficult in the field... with an on board welder.

nakman
04-09-2012, 01:05 PM
All this and no one has asked "Nak, whatcha' welding man?" I am interested in what you are up to? :D

there's a cross member for the Asfir skids that is pretty weak to me how it attaches to the frame. So I'm staring at it thinking of what kind of new bracket I could make, or should I drill/tap into the frame, then starting thinking huh I could just zap it on for good and call it done? Even adding grinding it off later to the equation, when/if I had to swap a t-case or something, I'd still be time ahead.

DaveInDenver
04-09-2012, 01:19 PM
Um, the starter crank position doesn't take the ECM out of physical connection, does it? I thought the starter crank position turning off electronics was mostly to conserve current capacity... ?? And maybe keep voltage fluctuation damage from happening to that nice stereo due to draw down while cranking?

Taking the ECM out of physical connection would make welding to one's own vehicle a bit difficult in the field... with an on board welder.
The ECU obviously can't be taken out of the circuit when cranking, so that's why they put TVS diodes in them. Most electronics do not have (or have insufficient) protection and that's why they're put into a safe condition. I guarantee no manufacturer have ever bothered to consider the effects of an on-board welder on their electronics. Remember we're talking peak power, not average. Sure, you can roll the dice, just giving my $0.02. Take a close look at the datasheets. They're going to tell you a TVS is capable of, say, 5KW, but that's at very low duty cycle (like 0.01%) with a repetition rate of probably on the order of 10 hits within 1ms or so.

Red_Chili
04-09-2012, 01:42 PM
I'm pretty sure the manufacturer never considered the use of a solid front axle, soft top, cut down doors, high capacity power steering pump, 3.4L V6 swap with supercharger, R151 tranny, double transfer case, 4.88 gears, and 35" beadlocks in their mechanical engineering analysis either, so if that is the safety rail I'm already off the highway and hanging over the abyss...

As evidenced by the need to beef up the front crossmember or fracture the frame. Typical mod.

Let me ask another way... how many ECMs have been zapped by on board welding (following basic common sense cautions)?

nakman
04-09-2012, 01:51 PM
In the spirit of clarity, when you say "on board welding" are we still talking about welding something onto the actual truck? Or are you talking about firing up your Mobi Arc out on the trail?

OilHammer
04-09-2012, 04:07 PM
Reminds me of a "funny" story. Back in the day, we had a history of tackling HUGE amounts of fab projects for club members the weeks leading up to GSMTR. We often took the whole week off in anticipation of the event, though the weekend before was always welding up something new and crazy into the wee hours of the night. Last time I remember doing one of these all-nighters, we decided to get the fab guy's truck up and running. It was a spring over, it was late....welding clamp went on the frame, made a few welds for some linkage mounts, then decided to weld on the rear axle. Neither of us remembered to move the grounding clamp to the axle. Well, short story, the braided SS brake line became the ground...and it lit on FIRE. He threw in the towel for the night after that, and I'm not sure he ever got the truck running either.

Beater
04-09-2012, 04:33 PM
Not by a mobi arc or the like, But I have personally seen a ecu fried by smaw to the frame. of course, that involved ac and a stuck rod and an idiot, but none the less.

Red_Chili
04-09-2012, 05:23 PM
In the spirit of clarity, when you say "on board welding" are we still talking about welding something onto the actual truck? Or are you talking about firing up your Mobi Arc out on the trail?
Yes.
The latter as an illustration of worst case of the former. Or in my case, Premier PowerWelder.

Red_Chili
04-09-2012, 05:24 PM
Not by a mobi arc or the like, But I have personally seen a ecu fried by smaw to the frame. of course, that involved ac and a stuck rod and an idiot, but none the less.
Details!

Air Randy
04-09-2012, 07:35 PM
Reminds me of a "funny" story. Back in the day, we had a history of tackling HUGE amounts of fab projects for club members the weeks leading up to GSMTR. We often took the whole week off in anticipation of the event, though the weekend before was always welding up something new and crazy into the wee hours of the night. Last time I remember doing one of these all-nighters, we decided to get the fab guy's truck up and running. It was a spring over, it was late....welding clamp went on the frame, made a few welds for some linkage mounts, then decided to weld on the rear axle. Neither of us remembered to move the grounding clamp to the axle. Well, short story, the braided SS brake line became the ground...and it lit on FIRE. He threw in the towel for the night after that, and I'm not sure he ever got the truck running either.

:lmao::lmao::lmao: I'm laughing because I did the same exact thing on the Blue Mule when I first got it, thought the whole truck was gonna go up in flames!

Air Randy
04-09-2012, 07:36 PM
I've always been too lazy to disconnect ECU's, etc and I have welded tons of stuff on my new diesel truck and everything in between and have never damaged an ECU (knock on wood).

rover67
04-09-2012, 08:26 PM
only thing I have actually seen is an alternator quit working. that may have been coincidence. It was after not disconnecting anything on a truck and having a muffler shop go at it.

bgoodheart
04-09-2012, 08:56 PM
I would NOT disconnect the battery... it acts as a clamping device. Think, capacitor. Shunts spikes to some degree.
YMMV.

Yep. Leave the battery connected. Every pro I've ever asked has recommended it for the reason Bill gave above. I use a surge protector on the battery as well. It may be snake oil, but it makes me feel better about things (like the ECU) in case my ground is compromised for some reason.

Here's the SP I use: http://www.otctools.com/products/antizap_auto_surge_protector (http://www.otctools.com/products/antizap_auto_surge_protecto)

If you look around, you can find them under $70 on occasion. I never had any trouble before I used one, but I have an ECU and a decent stereo to worry about now, and I like to worry. Ask Air Randy...


BJ

bgoodheart
04-09-2012, 08:58 PM
only thing I have actually seen is an alternator quit working. that may have been coincidence. It was after not disconnecting anything on a truck and having a muffler shop go at it.


Muffler shops are notorious for less than stellar grounds. They seem to be a recurring theme in most stories about fried components during welding.

Rzeppa
04-10-2012, 11:39 AM
I've always welded without anything special other than grinding a shiny spot for the ground clamp near where the work is being welded. Just did some rust repair to my 60 on Sunday. When I get her back from the paint shop I will be welding sliders on.

Main main thought process when welding on my rigs is just thinking about the current path. As long as there isn't anything sensitive in the current path then there's nothing to worry about.

Air Randy
04-10-2012, 02:21 PM
Yep. Leave the battery connected. Every pro I've ever asked has recommended it for the reason Bill gave above. I use a surge protector on the battery as well. It may be snake oil, but it makes me feel better about things (like the ECU) in case my ground is compromised for some reason.

Here's the SP I use: http://www.otctools.com/products/antizap_auto_surge_protector

If you look around, you can find them under $70 on occasion. I never had any trouble before I used one, but I have an ECU and a decent stereo to worry about now, and I like to worry. Ask Air Randy...


BJ

True Dat :thumb: but better safe than sorry eh?

Red_Chili
04-10-2012, 02:48 PM
Here's the SP I use: http://www.otctools.com/products/antizap_auto_surge_protector
BJ
I got all excited but got a 404 on your link...

Aha... fixed. Missing 'r'.
http://www.otctools.com/products/antizap_auto_surge_protector

Found this source for it too:
http://www.ntxtools.com/network-tool-warehouse/OTC-3386.html

The Sears version of it must be pretty darn special. Wonder if they sell a lot of those?
http://www.sears.com/shc/s/p_10153_12605_SPM6123743107P
:lmao:

Hmmm... different unit. Attractive pricing. I bet it has nothing more than a bunch of MOVs and such.
http://www.denlorstools.com/home/dt1/page_21870_48/dent_fix_df-601_anti_zap_surge_protector.html

DaveInDenver
04-10-2012, 03:13 PM
I bet it has nothing more than a bunch of MOVs and such.
What do you think the OTC widget has in it? It ain't rocket surgery.

Red_Chili
04-10-2012, 03:29 PM
Yeah, my comment was really about all of them. OK Dave, throw together a parts list of appropriate MOVs and/or other varistors and let's source and build them! RS fundraiser??

All fun and games till someone roaches something and it's (perceived as) our fault...

Rzeppa
04-11-2012, 10:12 AM
Most of the COGS is going to be in the cables and clamps. MOVs are like $0.50 or so, solid state TVSs will vary depending on power rating, but they're still pretty cheap. Most of the price (as opposed to COGS) is going to be in the markup. Specialty electronics devices (as opposed to commodity stuff) are typically around 70-90% margin.

TIMZTOY
04-11-2012, 08:39 PM
ive never had a issue when welding on motor vicheals. ive done tons of fab and repairs to this current truck and never had a issue or even though twice about it. because its direct current the flow will always take the path of liest resistance. same circumstance as the car getting hit by lightning, car keeps running.

I've welded repeatedly to the Chili and others with no concern for the ECM. I would NOT disconnect the battery... it acts as a clamping device. Think, capacitor. Shunts spikes to some degree. We are dealing with low voltages, but much current/ inductance. Operate accordingly.

Ground very close to your work and make sure you know what is near the welding location. Do NOT drape welding cables over anything, induction is real.

YMMV. agreed

All this and no one has asked "Nak, whatcha' welding man?" I am interested in what you are up to? :D
diddo