arc welding on a vehicle

[skylarkguy]

Hi folks,

I'm pretty new to welding. I picked up a used Miller thunderbolt AC/DC machine. It seems to work OK and I have been practicing some...it's coming along. My question is this.

I want to attach some D-rings or hooks to my Frankenstein dump truck (84 Chevy) besides disconnecting the battery what else should I be concerned with when welding to a vehicle?

Thanks

 

[Haywire]

Be aware of where your vehicle wiring is running. I bought a car once that had some welding done on it and the wire run behind the panel they were welding on melted.

Ian

 

[Joe H]

The alternator too.

Joe H

 

[Craig Clayton]

I would suggest that you keep the ground ( the other lead ) as close as possible. I even clean the local area for the ground to make the best possible contact.
The reason being current could flow bearings and harm them.

Craig Clayton

 

[N7943h]

Welding to the frame will weaken it from the heat which is why you see items bolted or riveted to frame members. Just pulling the ground wire off the battery will protect the electrical.

 

[Canada_CT230]

In our old shop we used to just disconnect the battery terminal at first. That will protect the onboard computers. Alternately you can buy a welding gizmo that you hook to the battery and it protects the system too. We got one of those cause it was faster but for once or twice you'd be stupid to buy one.

Agreed about knowing whats nearby (think heat) and frame weakening! Electricity takes the shortest route so the ground clamp should not be on the front bumper when welding at the back.

 

[yomax4]

May not need to but I always Double Ground.

 

[sjb]

So how is disconnecting the battery going to protect anything? If you induce a voltage spike in to the wiring I would expect the battery to absorb a lot of it. It should provide a low impedance path for anything above the battery voltage. I can see how a surge suppressor across the battery could help.

As already mentioned you need to pay attention to the path from the welding rod to the ground clamp.

Stan

 

[Canada_CT230]

Go ahead and weld on a vehicle w/o disconnecting then. All those mechanics/welders probably don't know what they are doing anyway. An ECM for your car would probably only run a couple thousand dollars. Try & maybe fry???

 

[Canada_CT230]

So how is disconnecting the battery going to protect anything? If you induce a voltage spike in to the wiring I would expect the battery to absorb a lot of it. It should provide a low impedance path for anything above the battery voltage. I can see how a surge suppressor across the battery could help.

As already mentioned you need to pay attention to the path from the welding rod to the ground clamp.

Stan

Cause when u disconnect you remove the electric wiring from the frame (ground) of the vehicle. Therefore there is NO voltage going down the wiring. When u leave stuff connected it completes the loop.

 

[Car Doc]

I take the ground cable off at the battery and I try to keep my ground lead on the welder as close to and on what I am welding. I have done it for 25+ years no problems yet but ymmv.

 

[roygage]

Hi folks,

I'm pretty new to welding. I picked up a used Miller thunderbolt AC/DC machine. It seems to work OK and I have been practicing some...it's coming along. My question is this.

I want to attach some D-rings or hooks to my Frankenstein dump truck (84 Chevy) besides disconnecting the battery what else should I be concerned with when welding to a vehicle?

Thanks

Twenty five years ago when Computers in cars were relatively new every automotive class I went to they would preach not welding on the car without unhooking not only the battery but the computer itself ect. Lot of horror stories by the instructors.

About this time I was looking into a muffler business to go along with my auto repair business, this brought me into contact with a large muffler shop to check things out.

I noted they welded on all the mufflers the only precaution being hooking the ground close to the work, I also noted there was no trail of stalled cars leading away from the shop.

One day asked a GM instructor I knew well about it, he said just get the ground clamp close to the work and no problem. Since have never even bothered to unhook the battery, never had a problem.

Don't do a lot of welding on cars but twenty times a year maybe, for twenty five years.

Unhooking the battery may still be a good precaution but unhooking it can cause some grief also on the newer cars.

 

[Redneck in training]

Welding to the frame will weaken it from the heat which is why you see items bolted or riveted to frame members. Just pulling the ground wire off the battery will protect the electrical.

The reason frames are riveted is different than you say. Welded frame has to be stiff enough that it would withstand maximum stress it is exposed to without cracking. It usually results in heavy frame like on in example on heavy machinery. Or it has to be three dimensional structure (cage) like in example racing cars. Since riveted joints can slip to some degree riveted frame will give up little bit but not break when overstressed.

 

[Canada_CT230]

Unhooking the battery may still be a good precaution but unhooking it can cause some grief also on the newer cars.

A dealership I used to work at many moons ago had a small 12V gel cell battery with alligator clips. They connected to battery terminals and then disconnect from car battery.

All the customers radio stations, etc. were still there mean while protecting the car's electrics.

 

[skylarkguy]

thanks for all the helpful responses. Sounds like the key here is to keep the welding circuit short. (ground close to the welding location) and protect whatever electronics are onboard. Unfortunately it may have to wait until spring as I just got it stuck in the mud this afternoon . My little mitzu will likely not pull it out.

 

[flusher]

A dealership I used to work at many moons ago had a small 12V gel cell battery with alligator clips. They connected to battery terminals and then disconnect from car battery.

All the customers radio stations, etc. were still there mean while protecting the car's electrics.

On recent model vehicles with a lot of electronic control modules, unhooking the battery can cause problems with these units (they have to relearn their settings). There are small battery devices called "memory savers" you plug into a 12V accessory port or your OBDII port and then disconnect the big battery. For example--

Amazon.com: Customer Reviews: SOLAR ESA30 OBD II Memory Saver Connector

 

[sjb]

Cause when u disconnect you remove the electric wiring from the frame (ground) of the vehicle. Therefore there is NO voltage going down the wiring. When u leave stuff connected it completes the loop.

When you disconnect the battery, that is all you are disconnecting, all of the electronic devices in the vehicle are still connected to ground. They are at risk of being damaged with or without the battery connected.

 

[sjb]

A dealership I used to work at many moons ago had a small 12V gel cell battery with alligator clips. They connected to battery terminals and then disconnect from car battery.

All the customers radio stations, etc. were still there mean while protecting the car's electrics.

So connecting a different battery somehow protects the cars electronics. How does this work. You haven't really changed anything except now you are running off a smaller battery.


The only way to guarantee that you won't damage anything would be to disconnect all the electronic devices. Given the large number of electronic devices in a modern vehicle this is not really practical.

Disconnect the battery if it makes you feel better, but you really aren't protecting much. The best you can do is to keep your ground path short, as has been mentioned. You also need to pay attention to your welding cables. You do not want to have the cable close to any of the vehicles wiring harnesses, as the magnetic field around the welding cable can cause voltage spikes in nearby wiring.


Stan

 

[workinallthetime]

Twenty five years ago when Computers in cars were relatively new every automotive class I went to they would preach not welding on the car without unhooking not only the battery but the computer itself ect. Lot of horror stories by the instructors.

About this time I was looking into a muffler business to go along with my auto repair business, this brought me into contact with a large muffler shop to check things out.

I noted they welded on all the mufflers the only precaution being hooking the ground close to the work, I also noted there was no trail of stalled cars leading away from the shop.

One day asked a GM instructor I knew well about it, he said just get the ground clamp close to the work and no problem. Since have never even bothered to unhook the battery, never had a problem.

Don't do a lot of welding on cars but twenty times a year maybe, for twenty five years.

Unhooking the battery may still be a good precaution but unhooking it can cause some grief also on the newer cars.

that was back in the day when SET class was 3 weeks long, if you remember that from gm training.

ive welded on everything from a 7500 series kodiac to durimax with 23 on board computers one of which is a highly sensative FICM.
i have always unhooked the ground cable (s) from the battery and let er fly. I am usually more worried about a fire than a fry, I always ground close and make sure its a clean ground. NO problems yet.
If its a 84 dumptruck i dont think there is much to worry about, the body control module will be the fella doing the welding, unhook the batteries and worry about the weld job