Welding on the frame

[Asross72]

I've searched around quickly on the forum and had a look at the resource guide (which isn't working on my iPad today for some reason), but can't find what I need.

 

I need to do some welding on the tail end of the frame, but can't remember what I need to do for the ECU.

 

Do I just disconnect the batteries or do I disconnect the ECU on the engine?

[GlennWest]

On my dually I just disconnected batteries. My bed builder for hdt removed my batteries.

[peety3]

Ask yourself a simple question: when the project is over, do I want to ask myself "why didn't I take a few minutes to do X?"

 

If you disconnect the ECU fully, you KNOW it's not going to get fried during welding. If you merely unhook the batteries, you only HOPE it's not going to get fried during welding.

[CrazyCooter]

I never understood why people think removing the batteries protects anything but the batteries........

 

I personally have NEVER disconnected anything while welding on any vehicles over my 25 year career of working on equipment, but I also keep the ground close to my work.....not a single failure of anything. Never use the engine or drivetrain as a ground unless you are specifically welding on them.

 

IF I were to disconnect anything just to be safe, it would be the BCM, ECM, ABS, etc and wouldn't bother with the batteries.

[NoDirectionHome]

The high frequency from a TIG can play havoc with CMOS stuff. With the cost of these electronics these days its a no brainer to get everything you know is on there disconnected. Can't fathom the cost of a DDEC or Transmission ECM. I've seen a TIG jog motors on machinery 30 feet away just from the radio waves it emits. SCARY!

[GlennWest]

Actually no high frequency unless tiging aluminum. Use straight polarity but still dc current

[SIBERNUT]

If the air bag pops, you'll wish you had disconnected the batteries. AND WAIT 10 mins for the residual charge to dissipate

[NoDirectionHome]

DC still uses high frequency to start Glenn

[GlennWest]

So you think you know more than a professional. Our machines has no high frequency on them. We tig. You can tig with any dc machine. Weld with ground.

[gjhunter01]

I have welded on many vehicles and never had any electronic issues. Electricity is lazy and always seeks the easiest path to ground, so make sure your ground is good, clean, and close to the spot to be welded.

Greg

[tyates007]

So you think you know more than a professional. Our machines has no high frequency on them. We tig. You can tig with any dc machine. Weld with ground.

Glen it would depend on your machine and features. I have machines that use a tig lift start on DC and also have machines that use a HF start with DC but only until arc strikes, not continuous like when on AC with aluminum.

[bstark]

I'm one victim of batteries that were still connected and welding done on the vehicle blowing the ground side of the ECM. A fully multiplexed 2004 International. The body builder managed to get a start condition by having a very experienced service tech friend put a small jumper wire across a couple of contacts, drove it to the dealer for an already scheduled maintenance appointment the following day, removed the jumper wire, closed her up, put the keys through the drop slot and waited for the phone call the next morning.

 

When call arrived and predicted conversation arrived at the point of "we couldn't get a start enable condition on your truck this morning" it was my cue to: "well gee, it was running fine when I left it in your yard last night.". Truck was brand new and still under it's full warranty so they replaced the ECM but whew; that was a close call.

 

I was having the toter body built and one last little bit of welding being done on the aluminum body was done without disconnecting the batts, et-voila. The tech explained ECM's are especially vulnerable to spikes coming in through the ground side of their chassis. He also claimed this was also a common result of someone allowing a wrench to contact chassis parts while tightening batt cable connections.

[GlennWest]

Glen it would depend on your machine and features. I have machines that use a tig lift start on DC and also have machines that use a HF start with DC but only until arc strikes, not continuous like when on AC with aluminum.

I know this. Been doing this 41 years. It's people tell me tig uses high frequency I have to correct this. We would never use such a machine with hf start cause we could damage very high dollar industrial equipment. Plus it would make arc marks that would have to be ground off. But I don't know anything according to ya'll. To the original op, only way I would not disconnect is to grind ground are and have a clamping ground. Ground directly beside your weld. Current can only flow between ground and positive.

[MsChrissi]

Not that we are professionals (we're not) but I think it is safe to say we have probably welded on our Volvo more than anyone else (hereabouts) has on a Volvo. We have used Miller Dynasty inverter TIG as well as Miller MIG on it. We have also used a Hypertherm plasma cutter where needed. We have welded all the steel on the motorhome body back there, The entire roof is 3/16" aluminum diamond plate in 8 panels and that was also AC welded while in place on the top. So I'd say we have done every mode but stick weld on the chassis.

 

A professional truck repair place in StL told Randi they disconnect the batteries and always place the ground nearby but always between the weld and the cab. To deal with built up charge they grind a bare spot and vice grip a chain to it that dangles to the floor.

 

We take it two steps further. First we disconnect the instrument cluster (because it is easy, but expensive to replace) and we take a watering bucket and douse the chain on the ground. I will also admit we ground to the same spot at the very rear of the chassis every time. We have never disconnected anything else.

 

Guys, that is a lot of welding by several modes. Can't speak for other brands, Miller and Lincoln have different TIG starter techniques but they can't be that different.

I think we can say we are past the point of just being lucky?

[peety3]

I know this. Been doing this 41 years. It's people tell me tig uses high frequency I have to correct this. We would never use such a machine with hf start cause we could damage very high dollar industrial equipment. Plus it would make arc marks that would have to be ground off. But I don't know anything according to ya'll. To the original op, only way I would not disconnect is to grind ground are and have a clamping ground. Ground directly beside your weld. Current can only flow between ground and positive.

Glenn, let's play a game of "what if" here. What if you've been doing it wrong for 41 years? Not saying you were, but what if? As my HS band director said, practice makes permanent, only perfect practice makes perfect. Just because you'd never use a machine with HF start, doesn't mean the next guy won't. Just because you're protecting high-dollar industrial equipment, doesn't mean truck ECUs are vulnerable to the same risks. And current will flow where it wants to flow...assuming that a particular ground is 100% perfect conductor is a recipe for disaster. It's the reason UHaul often has people do some zig-zags in the lot to scuff up the ball and improve the ground for the trailer lights. Painted frame rails can work the same way, which leads me back to my previous comment: just unplug the ECU, it's cheap insurance. Sure, you may have gotten lucky last time and every time before that, but if you want get good, unplug it every time.

[GlennWest]

Well I make 40 per hour and double pay for all premium time and that is after 8 hrs and all weekend and holidays. I am in high demand. If I doing it wrong believe me I will continue. I'm Not advocating not unhooking ecm, etc. Grind ground point, no paint, not rust and a good clamp type connector. Current will flow form a to b. Bad ground and it could fry the entire wiring harness. Recently I heard a fitter holler out. His welder had hooked the ground on the steel close by. They were tacking up a pipe 2" pipe joint. A length of #9 tie wire was used temporarily for a hanger near them. The pipe was carbon and rusty surface. It grounded thru the tie wire. Fitter backed into it. It was red. Ground will take path of least resistance.

[Ronbo]

I think we have multiple professionals that use multiple machines and multiple techniques. Instead of mine is better than yours, how about this is how I do it to prevent problems because of this. That is much more educational to me, a hobby welder that does weld on my truck. I am learning from each one of you and will change some things I do next time as a result of this discussion. I also realize I have been extremely lucky so far. Thanks guys and gals.

[HERO Maker]

I think what is really being said here is that taking all precautions necessary will ultimately save you a couple of systems (that would be very expensive to replace) and the time is takes you to prepare could payoff tremendously. And as Glenn even mentioned, the other welder (I would think that welder would claim he is a professional) did something that might not have been the safest thing to do, and someone else got hit!

 

So take all precautions that you can think about, and have heard stories on, and your day will go a lot easier and a lot safer for all (people and equipment).

[peety3]

Well I make 40 per hour and double pay for all premium time and that is after 8 hrs and all weekend and holidays. I am in high demand. If I doing it wrong believe me I will continue. I'm Not advocating not unhooking ecm, etc. Grind ground point, no paint, not rust and a good clamp type connector. Current will flow form a to b. Bad ground and it could fry the entire wiring harness. Recently I heard a fitter holler out. His welder had hooked the ground on the steel close by. They were tacking up a pipe 2" pipe joint. A length of #9 tie wire was used temporarily for a hanger near them. The pipe was carbon and rusty surface. It grounded thru the tie wire. Fitter backed into it. It was red. Ground will take path of least resistance.

Well I make >60 an hour salaried with fat benies doing Internet networking at a very large software company, and pocket 125-150 an hour doing network consulting on the side, with only 20 years in the biz, but the price of tea in China is still a variable. Paycheck aside, back when I was getting 0 an hour volunteering as a firefighter, they taught us a very important walking technique whenever we were near a ladder truck. On the off chance that the ladder was energized by nearby power lines (fire ladders can't be isolated, as they're plumbed for water and likely tied to ground through the hydrant), you should always jump off a ladder truck so you don't create an alternate path to ground. You should also take small steps when walking away from the ladder truck for the first 10', as even the ground isn't a perfect ground, and a long stride could easily create an alternate path to ground. Even frame rails are going to have a finite resistance, and the output side of the welder is sufficiently isolated from true earth ground, the frame ground could still have a potential relative to earth ground. If somehow the ECU manages to bridge that gap, it will transition into a WEU (wallet emptying unit).

 

All I really want to hammer home is it's better to be good than lucky. Be good about disconnecting the easy things, and that way you don't have to hope you'll be lucky.

[rickeieio]

All I really want to hammer home is it's better to be good than lucky. Be good about disconnecting the easy things, and that way you don't have to hope you'll be lucky.

 

X 2.

 

I built my bed, using Miller Mig and a plasma cutter. Unhooked nothing, but always kept ground very close to work. Maybe I got lucky.

 

In the future, I will "buy a little added insurance" by unhooking any modules.

[GlennWest]

Actually I have welded on hundreds of trucks. Mostly pickups. Adding hitches, etc. Never unhooked nothing. Never a problem. Don't believe I am that lucky.