Welding Around Automotive Electronics

Welding is not all steel frames, bars, butt joints, angles and sheet metal.  Sometimes you have to work on projects where you’re welding in close proximity to sensitive electronic gear that for one reason or another, needs to stay right where it is while you weld.  

A perfect example of this is automotive welding.  So in this situation, you might ask, “Do I have to disconnect the battery to weld on equipment?”  We’re going to say, “Yes.  Disconnect the battery before welding on equipment,” but there is some debate about whether that’s totally necessary.

Any time there is a forum of workers – many of whom considering themselves experts – there will be conflicting opinions about this or that.  Is that the best technique? Is that a good product? Where can I find, what is this for . . etc. And on the subject of welding, there is no shortage of disputes on how best to accomplish a task.

We’ll highlight the main arguments, pro and con, on whether you should disconnect the battery when working in conjunction with nearby or attached electronic equipment.  Working on cars is probably the time when most of you will encounter this situation, but there are plenty of industrial applications with similar factors.

Arcs and Sparks

Do you remember the phonetic device to memorize the color coding on a resistor?  You know, the thing with the “bad boys” and “young girls”? No? It’s OK. You won’t need that, but you will need to know a little about Ohm’s Law to understand this section.  And Kirchhoff’s Circuit Laws.

Car repairing

While the average welder might not worry too much about the numbers produced by these formulas, he should be familiar with the principles they represent.

Ohm’s Law

Ohm’s law is V=iR, or voltage equals current times resistance.  Simply stated, it means that the current running between two points is directly proportional to the voltage across those two points.  

When you weld, you’re applying current to a piece of metal, and that metal offers resistance. The welder doesn’t know the resistance value of the metal, for the most part, but he can calculate it for precise application of current during the welding process.  Some welders encounter the same types and sizes of metals over and over, and knowing their resistance value – even if it’s just in ballpark terms – can be helpful.

Kirchhoff’s Circuit Laws

This law states that the sum of voltages around a complete electric circuit must be zero, and the sum of currents in and out of a node on that circuit must be zero.  It’s not as complicated as it sounds. Imagine a jar full of marbles. Some are green and some are blue and you cannot add or subtract one color without making a proportionately equal change in the other color.  The sum of the two will always be the same. The change will always be zero.

Welding Circuit

Getting back to our primary topic, imagine working on a car equipped with some onboard electronic gear that you want to keep safe from harm.

The welder supplies the current and the car’s frame acts as a giant resistor. If you leave the car battery connected, voltage (remember, where there’s current and resistance, there has to be voltage) is applied to everything that is connected to the battery. That includes onboard computers, relay systems, the radio – anything in the loop.

It would not be out of the question that the voltage would reach over 100 volts.  That may sound a little high for welding applications, but the car frame is not as good a conductor as you might think. Depending on where you put your clamp for welding, the car’s frame could include a lot of transitions from one piece of metal to the other, and whatever devices are used to join those together – bolts, screws, hinges, plates, etc.- now impart their own level of resistance to the mix.

Those who claim the sensitive electronic gear would be safe from harm because it’s all grounded do not not consider the inconsistencies of the car frame as a conductor, which can cause voltage drops and spikes during the welding process.

When is the Risk Greatest?

flickrsendr by bunnygoth, on Flickr
"flickrsendr" (CC BY-ND 2.0) by bunnygoth

In a welding situation, the voltage fluctuates throughout the arc, but the most significant fluctuation occurs just as the arc is struck – that first powerful surge of current, light and heat.  It’s possible that during stretches where the voltage may temporarily stabilize you could weld without damaging connected electronics, but you can’t avoid that explosion of current at the very beginning.  That’s when the risk of damage is greatest.

Also, working with highly conductive metal, like the sheet metal on a car’s hood, may help keep overall voltages down, but that first strike of the arc is still a doozy!

Minimize the Threat

If there ever was a better-safe-than-sorry situation, this is it.  Whether you’re a seasoned pro or a DIYer, take the time to ensure that you’ve minimized the risk of damage to sophisticated – and expensive electronic components.

Here are some things to do:

  • Disconnect the battery’s negative terminal
  • Place the welder’s ground clamp as close as possible to the actual work section
  • Disconnect airbag connectors

We’re Positive; Disconnect the Negative!

When you disconnect the negative terminal on the car battery, you break the loop at that point.  When you disconnect the negative post, anything connected to the battery via the hot side, you provide some level of protection to those devices.

Conversely, when the battery is fully connected at both terminals, voltage from the welder passes through the electrodes in the battery, so therefore (remember Kirchhoff’s Law), the battery adds its voltage to that generated by the welding process and it all arrives at the various electronic components in a dangerously ramped-up state.

Keep in mind, electronic components remain somewhat at risk from the effects of the welding circuit, even when you disconnect the negative battery post.  They’re still grounded to the frame, and subjected to the same stresses it is, which makes the next tip very important.

There is risk even when you shut off the welder.  Welding creates a massive electromagnetic field. When you shut off the welder, this electromagnetic field collapses, and there is a chance that a brief voltage spike could race through everything that was near that field.

Clamp it Close

If possible, try to avoid having current racing around the whole of the car frame.  To accomplish this, place your grounding clamp as close to your work as you can. This minimizes the amount that the conductor (the car frame) shares with the things grounded to it.

You Don’t Want to Set Off That Airbag!

Don’t you hate it when that happens?  If there was any one singular reason why you would want to take all precautions before welding on a car frame, this would rank near the top.  While it’s not a likely scenario, there are so many circuits and sub-circuits in modern vehicles that a voltage spike could get into one of those circuits and poof!  

It’s even less likely that you would damage the electronics that serve the airbags, but it’s still very much worth the effort to disconnect the airbag system.  It’s not hard.

For most car and truck models, removing the fuse for the airbag will disable the airbag system.  In fact, owner’s manuals insist upon it when you work on the dash.

Going the Extra Mile

Since disconnecting the negative cable from the battery doesn’t totally isolate electronic gear from the voltage surges generated by welding on the car frame, you may want to go to the extra trouble of physically removing the items from all exposure – if possible. 

If they’re grounded to the frame by wiring only, disconnect the wiring.  If they’re connected to the frame directly through their own frame, take them out of the dash.

As to whether all of this trouble is worth it, only you can be the judge.  Consider all the possibilities, what you stand to lose if the worst-case scenario occurs.  Here are some factors to consider:

  • How long will the welding process take? If it will be over with quickly, the risk is less
  • What setting are you likely to use? Higher settings mean higher risk.
  • Where will the welding take place? The closer to the electronics, the greater the risk.
  • What is the value of the at-risk electronics?  If it’s standard-issue stuff, maybe it wouldn’t be the end of the world if it got fried.
  • Is there anything irreplaceable among the electronic devices.  If you have something that’s unique or out of production, it would be hard to replace.
  • How difficult would it be to physically remove the electronic devices? There’s a law of diminishing returns here, where you might be exposing electronic devices to a greater likelihood of damage during the removal/re-installing process than during the welding process.

Welding and Electronics in General

While we’ve been talking exclusively about welding on cars, there are many other situations where you might be welding in close quarters with sensitive electronics. They don’t have to be physically attached to the welding circuit to be at risk.  

Electromagnetic radiation can interrupt, alter and permanently damage certain types of electronic devices, and the welding process generates tons of it.  Theoretically, the electromagnetic waves could mess with computers and the power supplies they draw from. Pacemakers could receive unwanted interference. There have even have been instances where welders’ electronic watches showed the wrong time at the end of a work shift! The probable cause: electromagnetic interference.

Protecting Electronic Devices

Increase the distance between the welding and the electronic devices if you can. If not, protect the electronic devices as much as possible.  And that’s easier said than done.

One of the best things you can do is to make sure the arc welder itself is properly grounded.  Don’t confuse this with grounding the welding circuit, but grounding the machine itself.  Some seasoned welders are dissatisfied with the term “grounding clamp” on the welding circuit. It sometimes gives novice users the notion that it’s the only grounding that is necessary.

Wrong. You must ground the welder separately from the welding circuit. In many cases, you can ground it to a large metal work table, or a metal building frame. It has to be metal, however.  Since electricity takes the path of least resistance, grounding the arc welder puts it on the same level as other grounded components.  

Some welding units – especially new generation ones – generate extremely active high frequency signals. This is due to the various circuits within. TIG units are particularly troublesome.  The voltage in these circuits don’t usually match the voltage generated in the welding process and the imbalance can cause high frequency signals to radiate away from the welding area.  Follow grounding recommendations from the manufacturer to reduce EM radiation.

You Might be at Risk Too

EMFs (electromagnetic fields) can possibly affect you as well.  Research dating back more than 70s shows a connection between health and exposure to EMFs during welding.  The report cites alleged links to cancer, sterility, heart problems and neurological damage.

The American Welding Society disputes this assertion, and in 2015 stated:

Many scientific tests have been, and are still being, conducted by governmental and private agencies to determine if EMF is harmful to our health.  Studies to date indicate that there is no confirmed evidence of health problems from EMF.

The best advice here is to learn more about EMFs and how best to mitigate their effects.  EMFs swirl around us, and they come from more sources than just welding. Any time we make a call on our cell phone we expose ourselves to EMFs.  TV sets, computers, appliances, wiring – especially out-of-code wiring – can exude EMFs.


There’s no substitute for safety, whether you’re protecting electronic devices or yourself, and there’s no reason to charge ahead with a welding project and ignore prudent advice.

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