dieselfuelonly

Hey guys, quick question for you:

I was working on getting my exhuast installed today, and I had to make up a hanger to hold the stuff together. At first I was going to bolt the new hanger to the truck, but there wasn't enough space so it just ended up that the hanger got welded to the underside of the truck.

I don't know a whole bunch about welding, I'm definatly a newbie at it. I was talking with Box5 tonight and he was like "you did disconnect your battery cables, didn't you?". I was like um..... then really bad thoughts filled my head about what may have happend to my truck, lol.

The welder was grounded to one of the framerails under the truck, and the hanger was being welded to one of the supports that crosses the framerails towards the very back of the cab. (This is on my 3500, which has a reg. cab).

Anyway, I got in the truck and took it for a drive and everything seemed fine earlier today, but of course I hadn't even thought about what may have gone wrong.

The truck started and ran fine and did everything normally like it should except for the huge BGGGGGGGGGGGGGGGRRRRRRRRRRR that came out of the exhaust whenever I put my foot more than 1/2" into it .

Just in case you didn't catch what I said above, I DID NOT disconnect the battery cables.

So does that mean that everything is OK?

I hope this is just one of those "lesson learned" things .

Thanks,

DFO

Luvnacumns

Oh man I hope you didn't fry your puter!!! Or any other damage!! I have almost forgotten to unhook my batteries before too but caught myself!!!

Good luck!!

dodgeguy71

Yes it would appear that all is well with your truck. Yes they do say to disconnect the battery cables because voltage/amp spikes could go back and wipe out your $$$$ ecm. Do us "professionals" always disconnect the battery cables when welding in new cats on $50,000 plus Cadillacs......no. In all my experience welding on cars,trucks, heavy equipment I have never fried a computer while welding. I always clean off a spot, down to the metal for my ground clamp as close to the weld as possible. Remember, the path of least resistance thing?? I figure if I am 6 inches away from my weld with the ground clamp with a good clean connection the voltage will go there and not through your battery ground cable, through the battery and on to more pricey parts....to much resistance to overcome. Just my thoughts.

We never disconnected battery cables or fuses when replacing airbags either. No one I know or who they know has ever had one deploy in their face. That was in the fast pace world of flat rate however. Sometimes being safe than sorry always comes into the picture though. From what you said it sounds like your truck is fine.

Shawn

bigwhite59

it's possible, in theory. But it's never ever happened to me, same as above, i was in the performance business legitamitly for about 5 years, and a couple years prior, welding on cars ranging from 5000 dollars to 175000. The only problem it would cause on your truck, is the gauges would act goofy or not at all, and the trans may not go into OD if it's a 47RH auto. That's pretty much all the ECM on the 12v trucks do.

tbarbee1

Youre fine Im a pipeline inspector/welder and alot of the welders including me have their welders grounded to there truck so they dont have to string out the ground to weld on the back of their rigs they just put fittings in the vice and got to work be glad its not a ford or it would not have started after the welding it will definitley fry the brains on a ford even with the cables disconnected not sure why but I have seen three guys do it.

chaikwa

Well, I hate to be the bearer of bad news, but it IS possible to fry stuff when welding on a truck, car or piece of equipment. I've done that several times before I learned my lesson. One was a Cat computer on an excavator which cost me about $1500. Another was on a Komatsu dozer. Still another was the TPS on my own 93 Dodge. 3 times on the Dodge before I learned!

I think I've posted this here before, but I'll post it again. It's from part of an article I wrote for a welding publication and it kind of explains the whole 'disconnect the battery before welding' theory.

Protection of Vehicle Electronics While Welding

1. I have been operating a portable welding business for 20 years now, and without fail, if I weld on the back of my truck, (93 Dodge diesel), and do NOT disconnect the battery, the electronic Throttle Position Sensor becomes inoperative. I have fried this little component 4 times now.

At first, I held many of the opinions that have been expressed by various welding professionals; keep the ground clamp close to the work area, disconnecting the battery causes more problems then it solves, etc. But since I started disconnecting the battery, (when I remember!), I haven't had any more problems.

As for explanations of WHY things 'fry', maybe this will help;

Electrical components are at risk NOT from the normal voltage and current given out by a welder during use, but instead from the very large voltage spike that occurs unavoidably when the arc is switched OFF.

This spike occurs because the high current path through the welding cables, the weld pool and the arc itself will set up a significant electromagnetic field around itself. When this field collapses very suddenly as the arc is switched off, it will induce a voltage pulse in nearby electrical circuits even if they are electrically isolated from the actual welding current path.

The size of this pulse is determined by a whole host of factors, but long connecting cables are particularly good at suffering from this induction effect, hence the need to disconnect them from sensitive circuits.

The welder's transformer itself also generates a big spike as its electromagnetic field collapses when the arc is switched off. This is directly carried into the component being welded and so distributed to anything connected to it.

Some mechanics disconnect the battery during welding in the mistaken belief this will protect those sensitive systems on the vehicle from voltage spikes. Others think that positioning the welding ground clamp near to the weld area will offer protection. In fact neither of these methods offer 100% assurance that the voltage spikes will not cause irreparable damage. The only way to guarantee protection is therefore one of three ways in order of effectiveness:

1.Remove the object to be welded from the vehicle and weld it before refitting it.
2.Fit a surge protection device to the vehicle being welded.
3.Disconnect all sensitive equipment from their connecting cables.

Having said all this, welding on a vehicle without taking such precautions doesn't mean it will always be damaged. It does however mean you are risking damage and given the cost of replacing components you have to ask yourself whether it’s a risk that is really worth taking.

chaikwa.

wannadiesel

I think he's messing with you, guys.

Re-read his "problem".

Redleg

On that note, I've had issues with my instrument panel, ever since I left your place last. I have to beat on it to be able to check my speed at times. And I KNOW we unhooked the battery. I am researching how to retro fit it with the earlier gauges anyway, I hate the electronic. As a back-up, I think a guy on Ebay has rebuilds with a warranty on the electronic, the gauges are too vague.

Fronty Owner

a bad resonance perhaps. but if it runs fine, the electronics are fine.

chaikwa

You mean I typed all that out and he didn't really HAVE a problem?
J/K!

Yeah, so sue me! It's a Chevy... it prob'ly doesn't produce enough power in the first place to make the guages work anyway!

Got all your pics Don. I'll peruse them tonight.

's ready!

chaikwa.

BC847

Back in the day when real automobiles had a battery, coil, distributor, and plugs, (or less ) the concern of welding on the vehicle came from the threat of an errant current bridging a bearing or journal somewhere bonding the two together.


.. . . . oops!

Redleg

I think that's why they went to electronic gauges. They didn't want to rob it of valuable rear wheel horsepower by having to turn over a speedometer cable and a dial.

bentwings

I've done a lot of welding on cars and trucks over the years and not had any problems. Clean ground close to the weld is the rule. Electrically I can't give any clues , just what I was taught many years ago. Possibly the high freq from TIG might do some harm...I've done a lot of it probably most of my welding with TIG and not had problems. I have heard that high freq. can damage a magneto. I'd have to see it to believe it. I ran mags for a long time and not had problems. I welded exhaust hanger on my current truck and it's fine. Let's see some documentation and tested, repeatable facts.

ckt_santiago

I personally ALWAYS disconnect the battery cables before welding on my truck... I've seen people blow out taillights with the spikes from breaking the arc! That's how bad welding can effect your electrical system

dieselfuelonly

Well luckily, everything seems fine. Went for a drive tonight to wake up the neighboorhood , and there was nothing wrong with it that I could tell.

I'll make sure to remember to remove the cables next time!

Thanks for all the responses,

DFO.