Battery Disconnect

[Brianstick]

Is it true that you need to disconnect the battery on newer vehicles before welding on them?

[txfireguy2003]

That's what I have heard. Has something to do with the computer system onboard, like you might fry it if you weld without disconnecting the battery. I do know for sure that, before I had a welder, I took a couple of trucks to the welding shop to have bumpers welded on and they came back with the radio deprogrammed, I assume that is from them disconnecting the battery. In any case, how hard is it to disconnect that battery, seems like a good insurance policy junk in case, a new ECU computer for your vehicle would be a HUGE expense.

[Sberry]

I don't do it, ground on or near your work. This could be a long discussion but battery disconnects can cause their share of problems and thousands of work trucks are welded on every day without issue.

[hankj]

I'm like Cary. I leave the battery connected.

The downside of killing DC power to your cars "brain" can be as bad as frying the chip! All the counters rest, for one. You'll often get a "check engine" light, which, unless you have a code reader and the know-how to reset it, will likely cost you $70 bux or so for the local garage to reset it.

Keep the weld current circuit short (work lead next to the work!) and weld on.

Hank

[AnotherDano]

Back in my RV days, there was a little setup that was used to keep the clocks working - (and computers etc).

It was nothing more than a cigarette lighter plug with a battery pack hooked to it.

The instructions were to plug it onto the lighter socket and disconnect the ground from the battery, as I recall. Maybe the positive also...

Must have had a diode built in there somewhere to keep the vehicle battery from connecting to the unit's battery.

Anybody recall seeing one of these?

[Sberry]

We had this talk earlier and one of the engineers did help with this but how would taking the battery out of the loop help anything? Most of the danger is ground wires, theres is so much plastic in cars anymore that all these harnesses have ground wires.

[enlpck]

Just disconnecting the battery does nothing to protect the electronics, and may help protect the permanently connected electronics.

There are a few vehicles now where the manufacturers DO require disconnecting the battery on newer vehicles (last two to three model years), but, along with that, they also require disconnecting several harnesses as well.

If you connect the work lead adjacent to where the weld will be done, there shouldn't be a problem. Most of the horror stories I have heard have had more to do with bad technique than anything else.... connecting the work lead to th alternator to do a frame weld (this was an ASE instructor, of all things), things like that.

[Graham Brown]

Is it true that you need to disconnect the battery on newer vehicles before welding on them?

I believe you will mess up the computer, even if it wou't it takes litle effort to disconnect it

[TOMWELDS2]

Remove the part to be welded from the vehicle!..:p

Having an understanding on how electrons flow..I cant see any damage with ground clamp close to the work. disconnecting the battery would isolate and save the battery(??)...not the electronics

[J Hall]

FWIW,
My truck is a 2002, cd player, business band radioo, phones, Dewalt charger, etc.

I weld and airarc on the bed, usually wth the ground on th front of the bed,
Engine running or not, radios powered up or not. NO computer or elecrical problems at all.

[ShieldArc]

I weld on my 2002 chevy all the time, i just ground the part im welding. I remember a guy with a newer Dodge saying everytime he welded something on his tailgate the reostate on his gas pedal would fry. :confused::D

[Rocky D]

There is more of a danger of hydrogen gas exploding from the battery than frying the computer....keep sparks away from the battery...just cover everything with a fire blanket. Be safe!

[Sberry]

I agree. Lots of battery accidents (blew one up myself and was lucky, long time ago.) Especially after charging, charging a failed battery or one low on water I guess, lots of things including jump starting and disconnecting for service work. I get to handle a quite a few batteries, just the nature of the business. Way more problems caused by other **** than problems caused by welding. In 30 yrs, worked on hundreds of cars, , trucks and pieces of equipment, probably thousands, most every work day, anywhere from thousands of small welds to weeks at a time, never really had a problem, none associated with electronics. I carry the work ground cable around with me on a car and if I am working on the engine I ground there, chassis there, same for exhaust work and ground to the pipe on the car, sometimes to the attachment piece if its isolated, only one route for the current to take.

[Rocky D]

How about the high freq start on a TIG machine,...do ya think that could cause some damage....I know Hi-freq doesn't follow the same rules as regular current.
I never TIGged on a vehicle so I don't know. I personally would be afraid to. I've seen what hi-freq can do.

[TOMWELDS2]

An easier question would be: "has anyone ever had a problem"?:confused:

[Sberry]

Good question Tom. Rocky, I tig on mine but its relatively rare and most of my stuff is older but I am sure there are guys doing alum from the bed of trucks.

[Sberry]

We had this before on the Miller site and a couple engineers go into it fairly extensively, would be a neat thread to find. My work on new cars is usually wire harness just as it would be on any piece of equipment. Bearing arc would be just as much a concern.

[Amos F.]

I had a combine that was not a year old, at the time. A problem on the corn head required a little repair ( a snout hinge got pulled off the frame, close encounter with a rather large chunk of concrete as I recall at about 6 mph). After welding the hinge back on i went back to working the machine. When I unloaded the bin into the truck the unload auger would not shut off (???????). I shut the engine off and started it back up auger was shut off. It did this every time. I of course complained immediately to the dealer who sold it to me. They could not figure out the problem but changed a 'gray box' under the operator console and the problem went away. I figured it must have been defective and forgot about the incident. About four years later the service manager says 'remember when your auger wouldn't shut off?'. We've now replaced a few of those boxes and always after someone has been welding on the combine. I had mentioned this incident when it happened to a car mechanic friend of mine and he said I should have unhooked the battery, which I did each time after and have not had a problem since. All of my equipment with electric controls I disconnect no matter what. As for all the other ones, I just hook up the clamp and arc away on them.
Amos F

[TozziWelding]

I call BS, it is an old wives tail. I only disconect the battery when the guy paying me asks/tells me to(old timers). I beleive that the battery connected is a good thing, it will absorb stray volts/amps that could fry fragile components. I have a Ford with a computer controled PowerStroke motor in it. I weld on the bed all the time, 6 years later it is still fine, no fried PCM. Do what ever your heart tells you to do, as far as I am concerned it is crap.

[JD270]

iv seen it happen twice too s10 pickups and had the computer for the header control go out of one of our combines right after welding so i unhook the battery all the time on heavy equpment now and have had no problems since

[Aeroweld]

How about the high freq start on a TIG machine,...do ya think that could cause some damage....I know Hi-freq doesn't follow the same rules as regular current.
I never TIGged on a vehicle so I don't know. I personally would be afraid to. I've seen what hi-freq can do.


I've done quite a bit of aluminum TIG welding on vehicles. Mostly cracked transmission cases but also a few cylinder heads, intakes manifolds and blocks. I've never had a complaint of electronics problems after the repairs were completed. Sometimes the batteries were disconnected and sometimes not.
I do make sure that I fasten the work clamp as close as possible to the weld repair area to be sure there is no stray arcing.

[MrFriggsit]

I weld quite often on cars of all ages, and don't disconnect anything. Never fried anything. I have had problems after disconnecting batteries on newer cars though, like no starts, running problems, etc.. Most of the time there are too many modules to even think about disconnecting, so it's not practical.

[Old Man Stick]

Cant say about the new stuff. I just tell people to watch someone off road with a under the hood welder. Yep nothing like having the engine running and welding on the rig with its own ALT.

Years ago I was working as a Heavy Equipment operator. We had one of the dump truck in the bay to have the mechanic install a new hitch. Being fresh out of school and the mechanic being a clown he like to try to prove me wrong all the time.

So in front of the boss he asked me the same question. I said No you should not have to remove or unhook the battery. Well the mechanic went nuts on me. Saying all this crap would happen ect. Well he did his work and all. Had not even put his welder away and in front of the boss told me to get the truck out of his bay. I just nicely asked if he had hooked the battery up yet? The boss said thats funny I never even seen the mechanic lift the hood on the truck. Here the mechanic had never unhooked it.

So after all that I say on the older stuff like 5 years and back no .. the newer stuff maybe. .... My question would be is it paid off yet? If not ask the dealer. ;)

[small electrode]

Having repaired computers in an earlier life, I'd like to think I know something about electronics. Electronics obey the same rules of ohms law as the steel you weld on. Although electronics don't need much in the way of current to fry them. Voltage spikes or voltage above limits of the equipment will damage it. However, modern electronics, especially those in a hostile environment such as a vehicle, have snubbing circuits, shielding, etc. An old model car, just hook up the work clamp very near where you are welding and weld. That is probably more important than anything else. Attach the work clamp to the rear bumper and weld on the front bumper, and you just increased your chance of frying something. The weld current has to pass along the length of the car and the paths taken by the current are unknown, possibly through components you did not intend to.

The problem basically is a difference of potential (voltage) between two points, say your ECU (your engine computer) and ground. Leaving the battery connected MIGHT actually help protect the electronics as a battery is low impedance and would equalize the voltage difference between the + and the - as the current would readily pass through the battery.

However on late model cars there is really a small
"internet" interconnect of a lot of different "computers". To be safe here, disconnecting the computers from the cabling (power included) would be more prudent then disconnecting the battery as all the computers are connected together. Disconnecting the battery does nothing except remove a helpful voltage equalization path thus allowing MORE chance of damage.

Personally on an older car, I'd weld away. On a brand new car, I'd rather not, but if I could position the work clamp right on the same piece of structure I'm welding I'd probably do it, and I would not TIG with hi-freq on a brand new car. As mentioned in someone's elses post high voltage tends to do unpredictable things.

Sorry this grew larger than I intended.

SM

[aametalmaster]

I have never unhooked a battery in the 30+ years i have been welding on vehicles. I keep the ground close where i am welding...Bob