Welding on a vehicle

[The BN Guy]

I've heard people saying that welding on a vehicle has potential of frying the ECU (if equipped). I'm talking like welding on the frame or a bumper.

Is this true? The only proof I really have is the incident involving the BMW motorcycle from Long Way Round. They had to weld up a break in the frame and it fried his ECU. Yet I've seen people do it with no incident. How much in danger is the expensive lil bugger? I'm not sure how easy it is to get to mine but I do know where it is and I think it's not exactly easy to access.

Are there any methods to reduce the risk of frying an ECU? Does running a long bead run a greater risk than doing a tack weld?

 

[01tundra]

I welded on my Tundra for 10+ yrs with zero problems. I usually disconnected the battery, but didn't every time. I personally think it's either an urban legend or a very infrequent occurance.........

 

[cruiseroutfit]

I've made a practice of disconnecting the battery, both the positive and negative cables. I too have never seen actual damage caused by welding rather just the anecdotal stories of it. I can tell you just a few weeks ago I had to do some emergency welding on my Tacoma. We were in southern Utah when a random morning inspection on my truck yielded some very visible cracking and bending on my lower control arm. I had my Ready Welder good to go but as we were so close to Hanksville I swung into a known fix-it option and literally within 1 minute of pulling into the shop he was welding it up with a full-size MIG. He got about 10 seconds into welding before I thought about disconnecting my battery. No issues at all. Still, better safe than sorry I still pull the cables when I'm working on a customer vehicle.

 

[4x4x4doors]

I've seen it happen on a Zuki Samurai but the vehicle was relatively old at the time.
I usually go the route of unplugging the ECU just as a precaution.

 

[spencyg]

I never remove the battery cables when welding on a vehicle, and have never personally had any issues. I suppose if you were grounding your welder to the battery negative (absolutly don't do this!!!!) and were welding near the ECU you might introduce a current path which traveled through some critical input or output wires, but beyond this, I don't even see how it could provide the potential for damage. Current will always take the path of least resistance, and that path will be the frame and sheetmetal exterior.

 

[korslite]

Best practice to avoid running current through any of your electronics I generally to ground as near to your weld area a possible. As was already mentioned the current will always take the path of least resistance. As long as your ecu is not directly on that path you are good.

 

[LandCruiserPhil]

Exhaust guys never disconnect power on any vehicle. With that said I never have either and never had a problem.

 

[goodtimes]

I've heard the stories too - but like others, I've never had a problem. I've never talked to anyone who had first hand experience with something going up in smoke either - the stories always start with "my buddies, wife's, cousin's, best friend's, ex-boyfriend" . . .

I just make sure that I have a solid ground as close to the work area as I can. Electricity is going to follow the path of least resistance - so I give it an easy path back to the welder.

I do disconnect both battery cables - not that I can give a persuasive argument as to why, other than what I've read around the 'net. Considering how easy it is to disconnect them and how expensive it is to replace a ECU/PCM/what ever, I'd feel like a dumb-*** if I didn't & I let the smoke out of something.

 

[truck mechanic]

Had it happen to me, I was welding on a utility body of a bucket truck, ground rite next to my work, I ended up burning up the abs computor on an 4900 IH. So it can happen, now I ALWAYS diconect the batterys.
Paul

 

[bfdiesel]

As a note most current takes the path of least resistance not all. Also there is induced voltage in metal around the leads especially with AC.

 

[The BN Guy]

Excellent replies guys! That's exactly what I needed to know.

"Be safe and disconnect."

 

[LandCruiserPhil]

Can someone explain how disconnecting the battery does anything. The system is still tied together you are just minus the 12volt from the battery. Any foreign voltage introduced to the vehicles frame or body goes to the same places as far as the ground is concerned. Also any voltage introduced to the vehicle ground system will back feed through-out the system giving the same potential to the positive side at the unhooked battery.

Anyone?

 

[bfdiesel]

any voltage introduced to the vehicle ground system will back feed through-out the system giving the same potential to the positive side at the unhooked battery.

Anyone?

Exactly. Difference in potential is what is going to cause the problem. The problem is massive current flow and the battery will allow it to flow through it. Battery not connected no current flow from the welder or induced voltage will go through the vehicles electrical system.

 

[Buliwyf]

IC chips and other assorted electronics are more fragile when they are powered up than when they are dead.

An old tower tech showed me this. Touch a chip on a working control board and "poof", it failed. Deenergize that board remove that chip and do whatever you want to it, pop it back in and energize the board and it still works.

A welder with it's transformer can surge voltage just like a relay shutting down needs a surpression diode. That surge is short and hot just like static electricity. It can jump and wreck computer circuits.

Proper automotive computers should be built to withstand this. I believe they have a transistor of some type that drops out and disconnects/isolates the ECM from the main battery when you remove the trucks battery.

 

[98dango]

I have never cooked a computer. I have cooked brake lines I also never disconect the battery. My dad also has welded on a rig almost every day of his life and has never cooked any eletronics.