When welding on vehicle disconnect battery?

[KMinAF]

Just wondering, is disconnecting the battery when welding really necessary? I ask because if electricity takes the path of least resistance, then by placing the ground clamp as close to the work area as possible the welder won't be hunting for a ground through other parts of the vehicle. Second case in point, I have never seen a muffler shop disconnect a battery before welding.

 

[antinym]

I've welded on my car without disconnecting the battery and had no issues. Sample size:1 standard deviation:1.

I've heard stories of people having issues after welding, though. and disconnecting the battery seems cheaper than buying a new ECU.

 

[Buckgnarly]

Not ALL the electricity will take the path of least resistance. I usually try to disconnect to be sure. Not only electronics can fry, but be careful of fusing bearings and such.

 

[mambo]

i would

 

[KPSquared]

Why not take the 30 second effort on the off chance you shock some sensitive, highly over priced electronic component. I would just cause it's such an easy precaution.

Sent from my SAMSUNG-SGH-I997R using Tapatalk 2

 

[Jslys13]

I worked at an exhaust shop for about three years. We welded on 20-30 cars a day and never had a problem and never disconnected the battery.

 

[Grazz256]

I vote disconnect, mostly because I killed my battery by not disconnecting it. I wasn't doing a small amount of body/exhaust work though. I was replacing the back half of a frame...

 

[sberry]

Never, its no insurance against anything. Ground on your work. I have welded on 1000'sof cars, trucks, tractors, ships, even a couple air planes, ha. Not once an issue.

I worked at an exhaust shop for about three years. We welded on 20-30 cars a day and never had a problem and never disconnected the battery.

 

[purplezr2]

I believe its the TIG HF start that damages the electronic. A standard MIG will no damage it. Like

 

[Murphy4570]

I have welded on cars every day at a muffler shop for the past 3.5 years, have never had an issue.

Just don't put the ground clamp somewhere stupid, and you'll be fine. Don't use the vehicle's wiring as a ground circuit, put the clamp directly on what you are welding.

 

[StumpXJ]

Never, its no insurance against anything. Ground on your work. I have welded on 1000'sof cars, trucks, tractors, ships, even a couple air planes, ha. Not once an issue.

+1 for me

 

[garboui]

I have to disagree with the statement that "TIG is a problem because of HF but MIG wouldnt be an issue" While I agree that the HF from a TIG does create a much larger risk for electronics, the same thing that makes TIG hazardous also makes MIG hazardous.

When the TID is switching at a high frequency, the leads, electrode, workpiece will all have some magnitude of inductance associated. Being inductive the on/off high frequency will be creating many high voltage/frequency spikes at these on/off transitions. Now with MIG, the exact same thing is still happening except every time the current is started and stopped. While it seems like a comparatively smaller risk over TIG, semiconductors only need one spike to get past any TVS protection blow a crator through some junctions.

 

[sberry]

I have to disagree with the statement that "TIG is a problem because of HF but MIG wouldnt be an issue" While I agree that the HF from a TIG does create a much larger risk for electronics, the same thing that makes TIG hazardous also makes MIG hazardous.

When the TID is switching at a high frequency, the leads, electrode, workpiece will all have some magnitude of inductance associated. Being inductive the on/off high frequency will be creating many high voltage/frequency spikes at these on/off transitions. Now with MIG, the exact same thing is still happening except every time the current is started and stopped. While it seems like a comparatively smaller risk over TIG, semiconductors only need one spike to get past any TVS protection blow a crator through some junctions.

Ok,,, now explain how disconnectng the battery helps this.

 

[b-body-bob]

Ok,,, now explain how disconnectng the battery helps this.

I'm wondering how disconnecting the battery makes any difference since everything is connected through the chassis grounds.

 

[Heavy Metal Doctor]

I usually do disconnect the battery on most vehicles, but admit I do take my chance on some old, old stuff or very large machines where the power unit (engine / batteries / ecu) is far away / hard to get to.
Some specific "brains" require a full disconnect of all plugs before welding (Allison trans from 90's IIRC) or you "zap" the programming and the unit will not move again till reprogrammed ($$$$).

 

[NUTTSGT]

If I remember too, I'll disconnect the battey as precaution.


On the Mustang, I just flip the battery disconnect switch, piece of cake.

 

[Britt]

I'm wondering how disconnecting the battery makes any difference since everything is connected through the chassis grounds.

But, But, it protects the battery....

(Meanwhile it will still search for a way to complete the circuit, if you put the ground in the wrong spot, or it isn't a good connection due to anodize or paint).

 

[jdcompman]

I'm wondering how disconnecting the battery makes any difference since everything is connected through the chassis grounds.

+1 I was reading through this thread thinking the same thing!

 

[Olafur]

No, I have yet to hear/read any logical explanation as to how disconnecting the battery helps.

In my view - if anything - the battery offers protection. While connected it will short circuit static voltage spikes in the power loom offering protection to sensitive electronics. So IMHO disconnecting the battery in modern car is only justified if you also connect the positive lead to ground.

 

[rodknocker]

If your PCM is easily accessible pull the plug, it takes 2 seconds to save $1500

 

[GirlnAgarage]

On the one time I welded on the truck I did disconnect. Murphy's Law likes to attack my work so I figured at least I can say yes when I was asked, "Didn't you disconnect the battery?" heh

I just pulled the grounds off both batteries. Not a big deal plus you can have a look at your connections. I found one of my posts had some crud building up that I hadn't seen yet.

 

[sberry]

I did read or hear how disconnecting the + would help in some cases, it was fairly complicated and over my head but made some sense.

If your PCM is easily accessible pull the plug, it takes 2 seconds to save $1500

It would be one thing to fiddle with complicated connections if you HAD to but all this is purely speculation at best. Here we have a couple guys weld on cars daily, one dozens a week, as I said, in the thousands for me never had a problem.

Thousands of new trucks are used daily for work platforms by welders world wide, thousands is low, hundred thousand or more no problem.

Meanwhile its likely that considerable collateral damage occurs thru hook/unhook process and other fooling around daily, I can see this, someone reads this and starts yanking plugs, blow battery up in face in process, a dangerous act all its own, lots of potential problems.

 

[KMinAF]

A disadvantage to disconnecting the battery is everything looses it's memory and in the case of an ecm will require a period of re-learning. In my 30+ years of working on cars I have never had one come into the shop with electrical problems caused by welding. I wonder if it has ever been substantiated, maybe a good episode for myth busters?

 

[bmxr4life87]

Ive done plenty of welding on new trucks at work and have experienced no problems whatsoever

 

[wheats71]

My question is, is after you have welded a new muffler or tailpipe on a car for example and days or weeks later if drivability issues should arise, would customers return to the muffler shop or does anyone make this connection if indeed the is an issue ?
I know it is a rambling question but I wonder just because there are seemingly no reported issues, if there really are.
I am interested in the comment as well that the ecm grounds are grounded to the chassis, so does unhooking the battery really help?
I always have. There just seems to be a fifty fifty split on this

 

[torqueman2002]

My question is, is after you have welded a new muffler or tailpipe on a car for example and days or weeks later if drivability issues should arise, would customers return to the muffler shop or does anyone make this connection if indeed the is an issue ?
I know it is a rambling question but I wonder just because there are seemingly no reported issues, if there really are.
I am interested in the comment as well that the ecm grounds are grounded to the chassis, so does unhooking the battery really help?
I always have. There just seems to be a fifty fifty split on this

I see you are saying what I've been thinking as I read through the posts. "would customers return to the muffler shop or does anyone make this connection if indeed the is an issue ?"

It may very well take days, weeks for the 'welding with the battery connected' damage to reveal itself. And like the lightening analogy, damage can and will take different forms.

Disconnecting the negative battery cable is the quickest and safest way to open the vehicle's entire electrical system and isolate all connected components from transient spikes that can be generated by static discharge from simply sliding across a vinyl seat and touching a component's circuits/pins OR from spikes and/or induced EMF from electrical (not gas) welding.

Don't get me wrong, I do think you can weld on a car/truck and 'get away' without short/long term damage; but don't be surprised if there are unexplained symptoms down the road. It's like crossing a busy street with your eyes closed, yes you can get away with it for a while.

My first hand experience with something similar is testing GM car/truck ECM circuits destructively to validate the service information my group writes at the GM proving ground.

One test that will not give immediate sensor failure is to short +12V to the HO2S low reference (signal return) circuit. No apparent symptoms, no MIL, no pending DTCs. After returning the circuit to normal and operating the vehicle through multiple ignition cycles and days, the vehicle will set a P0171 /P0174 Lean Fuel Trim. Replacing the HO2S fixes the vehicle. No HO2S DTCs.

Think about the guy that can't be troubled to use a 9V memory saver when disconnecting the battery (or can't even be bothered to disconnect the battery) before working on your car. No thanks, not working on my car.

You may think this is just my opinion, and you'd be correct; but it is an informed opinion based upon working as a Powertrain Control Service Engineer since 1991.

 

[Murphy4570]

My question is, is after you have welded a new muffler or tailpipe on a car for example and days or weeks later if drivability issues should arise, would customers return to the muffler shop or does anyone make this connection if indeed the is an issue ?

Only once do I recall anyone coming back for that reason. Welded on a new muffler and tailpipe onto a Jeep....Cherokee? I think it was. Guy was happy, left. Came back a day or two later, saying that the dealer told him that due to us welding on the vehicle, his PCM was fried. We told him to go pound sand. Never heard from him again.

Our reasoning at the time was that the dealer couldn't figure out what the issue was with his vehicle, and played the blame game.

 

[3dkustoms]

Ive worked in body shops for almost 15 years now and have never disconnected a battery on one I was welding on unless I had to remove it for repairs. I have heard for years that you were suspose to but I have yet to have any problems. just my 2 cents

 

[Olafur]

[...]
Disconnecting the negative battery cable is the quickest and safest way to open the vehicle's entire electrical system and isolate all connected components from transient spikes that can be generated by static discharge from simply sliding across a vinyl seat and touching a component's circuits/pins OR from spikes and/or induced EMF from electrical (not gas) welding. [...]

Transient and EMF induced spikes have potential/voltage relative to the body/frame of the car. And the electrical system is usually grounded to the body, engine, (frame) in several places. Thus, removing the connection to the battery does not isolate the vehicle's entire electrical system nor isolate all connected components. The only thing that happens is you just unplug the battery from the circuit.

 

[torqueman2002]

Transient and EMF induced spikes have potential/voltage relative to the body/frame of the car. And the electrical system is usually grounded to the body, engine, (frame) in several places. Thus, removing the connection to the battery does not isolate the vehicle's entire electrical system nor isolate all connected components. The only thing that happens is you just unplug the battery from the circuit.

Sorry, but the other leg of the circuit is the positive to the battery, so even a component (ECM, BCM, ...) connected to chassis ground will be isolated in the sense there is not a complete circuit through the battery.

The purpose of disconnecting the battery is to isolate the sensitive components from the electrical surges that seek to complete their path to neutral potential through a component, back through the battery positive and battery negative; not to protect the battery.

Every required step in a service procedure contributes to the labor operation code and time paid for that code. The manufactures do not pay for unnecessary steps. In fact, there is a reward (Suggestion Program) for reducing any unnecessary steps/procedures in labor operation codes.

What reason do you propose the manufactures have for requiring battery disconnect?

 

[racingtadpole]

Edited to make it less simple for the flat earth society.

 

[MrMark]

Electrons absolutely DO NOT just take the path of least resistance. This is an uninformed common saying that attempts to oversimplify something that does not lend itself to being oversimplified. Electrons take all available paths in quantities inversely proportional to the resistance of the path. They return to the ground clamp on the welder of course but there are many paths they can take to get there. Hopefully, the other paths are of such high resistance relative to the shortest frame path to the gound clamp that few take other paths that could go through components grounding and complete through the battery back to the welder clamp for those that don't disconnect. Not disconnecting is foolish in my opinion.

 

[MrMark]

Sorry, but the other leg of the circuit is the positive to the battery, so even a component (ECM, BCM, ...) connected to chassis ground will be isolated in the sense there is not a complete circuit through the battery.

The purpose of disconnecting the battery is to isolate the sensitive components from the electrical surges that seek to complete their path to neutral potential through a component, back through the battery positive and battery negative; not to protect the battery.

Every required step in a service procedure contributes to the labor operation code and time paid for that code. The manufactures do not pay for unnecessary steps. In fact, there is a reward (Suggestion Program) for reducing any unnecessary steps/procedures in labor operation codes.

What reason do you propose the manufactures have for requiring battery disconnect?

Makes sense.

 

[MrMark]

I see you are saying what I've been thinking as I read through the posts. "would customers return to the muffler shop or does anyone make this connection if indeed the is an issue ?"

This is kind of like the plumber who never has any leaks.

 

[torqueman2002]

Edited to make it less simple for the flat earth society.

I think you are saying I 'splained it more better.

At least I hope that's what you meant, because that's my goal at work - take all the 'engineeringeeze' and boil it down to where we all can fix these increasingly complex cars and trucks.

Heck, I discovered some cars (not trucks yet, GM anyway) can set history DTCs with the ignition off. ¡Ay, caramba!

 

[GirlnAgarage]

Heck, I discovered some cars (not trucks yet, GM anyway) can set history DTCs with the ignition off. ¡Ay, caramba!

SkyNet

 

[sberry]

I think tech writers throw it in there because they think it and what could it hurt to unhook the battery. Kind of like when the electronic guys start talking about grounding.
So out of the hundreds of thousands of cars welded on every day we got a few that figure they know some secret , just in case, so we advocate a procedure in where there is no statistical data in favor of one where numerous problems occur including extra labor and exposure to battery explosion being one.

I have heard stories too, including a couple dandy's where a guy blew out every light bulb and ruined every part on the car etc. Like the man said,, 6 months from now a code setting issue and,,, it must have been welding is the conclusion jumped to.

Heck, I discovered some cars (not trucks yet, GM anyway) can set history DTCs with the ignition off. ¡Ay, caramba!

So like this,,, how can we connect this to welding? Another question,, where is neutral in the wiring system?

 

[sberry]

It may very well take days, weeks for the 'welding with the battery connected' damage to reveal itself.

Could take days or weeks for some random unrelated problem to occur too?

 

[torqueman2002]

... throw it in there because they think it and what could it hurt to unhook the battery. Kind of like when the electronic guys start talking about grounding.

Not throwing it out there because some tech writer thinks it; it is a verified failure mode. What kind of stats are you looking for? Anicdotal accounts are not objective.

I am not at work today, but if it is not GM propritary information I can post up imperical data, if you let me know for what you are asking.

Prior to the early 80's, when ECMs made their first appearance, there were few static discharge sensitive components (transistor radios, Chysler transistorized/electronic ignition?). There just was not the need for the precautions.

With the presence of ECMs and other low voltage/low current capable components, handling and other processes have updated to keep pace.

Check out the amount of voltage generated by a static discharge spark you get crossing the room in winter and douching something metal, it takes a surprising amount of voltage to jump from your finger tips to a object - that's the built up potential (charge) seeking a neutral potential (ground or less negative than your finger). Remeber - electron flow theory of how current flows; negative to positive. These are all relative potentials of course.

Prior to my current assignment, I maintained/programmed a computer system in Central NY for GM. When we worked on the circuit boards or the innards of the computers ground straps were required.

It's not imagined because it doesn't happen each and every time and it's effects are not immediately apparent. Think of child seats - certainly not needed most of the time, but you don't know when it will be needed and the conseqences are possible severe. lso, think about smoking - not every smoker will have problems, and it takes years. Do I statistics, no; but there's a body of evidence out there.

Breaking this up, to keep it readable.

 

[torqueman2002]

So out of the hundreds of thousands of cars welded on every day we got a few that figure they know some secret , just in case, so we advocate a procedure in where there is no statistical data in favor of one where numerous problems occur including extra labor and exposure to battery explosion being one.

There is no secret. Let me know what will convince you, I'll see what kind of information is available.

Yes it is extra effort to disconnect the battery, it maybe the car makers would rather pay for the extra warranty to avoid the possible component damage and customer dissatisfaction.

The car makers think in terms of 100's of millions of vehicles; if I work on a thousand before I die it will be a lot. Can you get away with out disconnecting the battery? Sure, there's no end of testimonials and 'tail light' follow up.

Exploding batteries? I missed that one. Is there a post here about that?

I know off-gassing from charging is a big explosion potenial. Disconnecting/connecting a battery negative cable will produce a spark if there is any current draw on the system. It's good pratice to wait for the off-gassing to dissapate before introducing any ignition source - spark, welding, cigarette, ...

Do you use jack stands each and every time you slide under a jacked up car? I know you can get 'away' without them; why do you take the time, and risk sinking them into the warm asphalt or banging them against the side of the car?