Will mig welding on chassis damage cars ECU?

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I need to weld some cracks in the exhaust system of a friends 1997 mazda 626 and was wondering if this is something I have to be worried about..any advice?
Reply:Exhaust pipe is not a frame.You can weld cracks in an exhaust pipe all day long.No problem.
Reply:Local exhaust shop never unhooks the battery, just clips the ground on the exhaust pipe and welds it.If you hook anywhere other than the exhaust pipe you're on your own Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:It all depends on how lucky you are. Most times you will have no problems.  but that one in ten you'll fry the ecu. Take the precaution and unhook the ground terminal on the battery. Five minutes or several hundred for a new computer. Better safe than sorry especially if it's not your car. Good luck! wear eye protection!!!Sent from my iPhone using TapatalkThermal arc 211iCk flex-loc 150 & 130Clamps, saws & grindersHarbor freight 80 amp inverter
Reply:You *should* be fine if your ground is located intelligently and has a good connection. On the other hand, a little extra caution certainly never hurt anybody...Aspiring Top-Notch WeldorLooking for work/experience in Eastern Massachussetts
Reply:Be sure to check for any fuel leaks or fumes before starting on this. Don't want to hear about no BIG BOOM.
Reply:You wont hurt the computer as long as you don't use the case of the computer to attach your work clamp.Or connect the work clamp to the front bumper so you can weld on the tail pipe.old Miller spectrum 625 Lincoln SP-135 T, CO2+0.025 wireMiller model 250 and WP-18V torchCraftsman 100amp AC/DC and WP-17V torchCentury 115-004 HF arc stabilizerHome made 4 transformer spot welderHome made alternator welder
Reply:Never had a problem with ECU connected, and have never run into anyone who has.  I only hear people talking about it.-AaronJet 17.5" Drill Press1942 South Bend 16x84 Lathe1980s Miller 320A / BP --- 2013 Power Mig 2562012 Jet 7x12 Horizontal BandsawVictor O/A Setup
Reply:Always disconnect the battery full I usually request that the battery be taken out. Prior to welding on any vehicle.Sent from my iPhone using Tapatalkif you can step across it I can weld it.
Reply:What about all those Guys that weld on the back of their trucks everyday? Do they disconnect the battery every time they weld? Cheers AndrewWIA 270amp Mig Transtig 200 AC/DC Tig/stickHypertherm PM45
Reply:I weld on trucks and cars frames and exhausts all the time never had an issue if it exhaust  as stated ground to where your welding
Reply:I request it because I don't want to be liable if it were to ever happen. Not a written rule. Sent from my iPhone using Tapatalkif you can step across it I can weld it.
Reply:I have never seen one killed but I have seen the tail lights com on when welding on the frame
Reply:Helped my brother put new rockers and cab corners on his ford pickup. We grounded in the area being welded. The truck would not start afterwards, fried the computer he found one in a junkyard for 300$. So it can happen, not likely but possible. His truck was mid 90s so it had one computer compared to newer cars with multiple computers. So like I said before better safe than sorry. Sent from my iPhone using TapatalkThermal arc 211iCk flex-loc 150 & 130Clamps, saws & grindersHarbor freight 80 amp inverter
Reply:Originally Posted by mad welder 4You wont hurt the computer as long as you don't use the case of the computer to attach your work clamp.Or connect the work clamp to the front bumper so you can weld on the tail pipe.
Reply:Originally Posted by Austin BennettHelped my brother put new rockers and cab corners on his ford pickup. We grounded in the area being welded. The truck would not start afterwards, fried the computer he found one in a junkyard for 300$. So it can happen, not likely but possible. His truck was mid 90s so it had one computer compared to newer cars with multiple computers. So like I said before better safe than sorry. Sent from my iPhone using Tapatalk
Reply:Originally Posted by HT2-4956+1The only time I take a battery out of a piece of equipment is if I'm going to be welding any where around where it's located.
Reply:I've relocated at least a dozen battery banks on larger trucks when adapting them for other uses and it's one of my least favorite things to have to do.  It just makes me nervous worrying about arcing something out to a terminal and getting burnt, flashed or having a battery explosion.   I always wear my heavy leather jacket, gloves and face shield when ever taking them off and putting them back in and hooking them up.  Another thing I learned kind of the hard way is that before you go un-hooking any thing it's best to make a decent drawing and get the ends of all the different wires numbered.  Because several days later when you go to hook everything back up that good mental picture you thought you took of how it was isn't going to be as clear as you'd hoped you'd remember it.   Arghhhhh!
Reply:Two thoughts.Running a large amount of current will generate magnetic fields - which in turn can induce currents in other wires.  Keep your work clamp close to the weld and minimize where the currents go.As for the battery.  A battery is an amazing damper of power.  Not only can in put out 200+ Amps for a few seconds (actually significantly more), but it can absorb those same 200+ amps and keep the voltages from going to high.  Like a surge protector.  That being said, modern cars are never completely turned off.  The computers are still running (security, remotes, clocks etc.) So it is possible that a live circuit sees some dirty power and blows.  So having a battery connected or not may help or may not.  It's a toss up.  If you decide to disconnect, give it a few minutes and let the air bags discharge (I think they recommend 15 minutes).BTW, when welding exhaust, I usually just tack it in place.  Normally one slip joint over the rear axle (there's a local shop that has even flaired a pipe on a Sunday for me...).   Final welding is done on the floor next to the car....  Even with a smaller MIG gun, with the hood down, I always seem to be bumping into something. When welding on the frame, I clamp near the weldCon Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:Originally Posted by con_fuse9Two thoughts.Running a large amount of current will generate magnetic fields - which in turn can induce currents in other wires.  Keep your work clamp close to the weld and minimize where the currents go.As for the battery.  A battery is an amazing damper of power.  Not only can in put out 200+ Amps for a few seconds (actually significantly more), but it can absorb those same 200+ amps and keep the voltages from going to high.  Like a surge protector.  That being said, modern cars are never completely turned off.  The computers are still running (security, remotes, clocks etc.) So it is possible that a live circuit sees some dirty power and blows.  So having a battery connected or not may help or may not.  It's a toss up.  If you decide to disconnect, give it a few minutes and let the air bags discharge (I think they recommend 15 minutes).BTW, when welding exhaust, I usually just tack it in place.  Normally one slip joint over the rear axle (there's a local shop that has even flaired a pipe on a Sunday for me...).   Final welding is done on the floor next to the car....  Even with a smaller MIG gun, with the hood down, I always seem to be bumping into something. When welding on the frame, I clamp near the weld
Reply:Originally Posted by SuperArc...can anyone please tell me which device exactly  is NOT protected nowa-days by a relatively low amperage fuse?   ...
Reply:Originally Posted by G-sonElectronics are sensitive mostly to high voltages, such as can be created by fluctuating magnetic fields (from welding) near the wiring harness. Fuses protect against high current, and are in electronic terms extremely slow = even if it would protect against the problem it would already be too late by the time the fuse has heated up enough to melt. A fuse is almost always only supposed to protect the wiring from overheating and burning due to too high current, they are rarely supposed to protect any equipment fed through the fuse. In other words, a fuse will not care if your ECU dies a horrible death from high voltage, but it will protect your car from going up in flames when the broken ECU starts consuming a hundred times the current it normaly does, and overloads the wiring...My uncle had a mid 80s Volvo 740 (no ECU, but basic electronic ignition) in the late ninties and had rust repair done to it. Started it at the shop, drove it home about 10km, parked it. Started it the next day, backed it out of the parking spot, and it dies right there - no spark. The electronics module for the ignition was dead. Too much of a coincidence, a 15 year old part does not die 15 minutes of driving after a potentially damaging procedure (welding) without being related to that. The rust repair killed it, just took some time for it to fail completely. Sure, it's rare, but it does happen.
Reply:Just put the ground in the tail pipe. You should be ok. The electricity will flow that way.