Welding and insulating a lift hook, or vehicle

[irnsrgn]

there are many welders/shopmen who would differ with you, who have blown up batteries or burned half the diodes out of alternators. In all my years of doing repair welding I had neither happen. If I was welding on the engine to remove broken studs usually I always had the mechanics disconnect the negative battery cable before I would ever attach my ground to the closest available spot to where I was gonna weld.

[arftist]

Afraid I have to agree with irnsrgn of this one. If the time it takes to undue one battery cable is too much to spend, then I guess you can readily afford to repair whatever damage may occur. Just because you have done something without ill effect, in no way garrantees that you will always get away with it. There is a concept that is a bar to all knowlegde; that concept is contempt prior to investigation.

[Joe H]

Give me a good explanation of how unhooking a battery cable can help.

Blowing up batteries? That's from sparking near a battery, nothing to do with the welding current.

You do need to use some common sense. Hooking up a work clamp on the front bumper and welding on the rear of the vehicle is just plain silly and begging for trouble. If your work clamp is near where you are working, and well connected, you will never have any trouble. Electricity doesn't just go roaming around aimlessly. It will take the path of least resistance back to your work clamp every time, with no interest in your battery or electronics.

I've spent quite a bit of time welding on vehicles with my TIG, using HF/HV start. If anything were going to cause problems that would.

[arftist]

I disconect batteries on cars with computers for the same reason I unplugged this computer from the wall outlet during the huge lightning storm we had here last week. Electrical isolation. Not connected, can't be harmed.

[Joe H]

You do realize that everything electric in a vehicle is connected to a common "ground", which is all the metal in the vehicle.

The only thing you are isolating by disconnecting the battery is the battery.

[Jose Gomez]

Ford knows best. Here is the ford welding procedure for post '04 trucks:
https://www.fleet.ford.com/TRUCKBBAS/non-html/Q114.pdf

Here is the ford welding procedure for post '05 trucks:
https://www.fleet.ford.com/truckBBAS...tml/Q123R1.pdf

Ford clearly states:
Models Affected: All F250-550 trucks; Model Year 2005 and later.
Action Requested: Please provide a copy of this bulletin to all Engineering, Manufacturing, Service, Parts, Sub-
Contractors and Customers that plan to use this vehicle as a mobile welding platform.
Background: F250-550 Instrument Cluster failures have been reported following plasma cutting or electric welding
operations. The 2005 F250-550 Instrument Cluster circuitry has proven to be more sensitive to
induced voltage. This includes service trucks intended as mobile arc welding platforms.

Warranty Statement: Before electric welding or plasma cutting on the frame or body of F250-550 units, disconnect the
battery, instrument cluster, ABS module and the PCM. Just disconnecting a battery cable is not
enough to prevent damage to these components. Damage seen in newly-constructed trucks has been
traced back to welding. Electronic module damage due to this customer or vehicle modifier action is
not covered in vehicle warranty.

Here is some manufacturer's instructions for welding on a Dodge
TSB 13-001-03

The fact that you have been lucky does not mean that it is good advice nor advisable to keep pushing your luck. Just because nothing bad happened the couple of times it was tried does not make it any less expensive when you finally do roast a computer or Instrument cluster.
Clearly, it is worth the 2 minutes that it will take to ensure that you don't void your warranty and end up accidentaly spending well over a thousand dollars (potentially)

[irnsrgn]

Dodge had a problem with their pickup front frames and came out with some weld on reinforcing plates. I did about 35 of these for the local dodge dealer, it was nice work, they had the trucks up on a lift, the front wheels off, all the stuff disconnected according to the instructions and the frames cleaned and the plates all in place with one pair of C clamp vise grips. All I had to do was add somemore clamps and weld them in place according to dodges print. As far as I know the only precaution was unhooking the negative battery post .

[arftist]

My first car disaster involved an aprentice who cut through a gas line with a torch. Complete new interior, I picked up the tab. Second time, replacing a section of frame, some type of tarred felt glued to the inside of the sheetmetal body, about six inches away from where I was welding, ignited, causing paint and again interior damage. The car owner was a machinist who was very understanding, but I still had to pay for the repairs AGAIN. Will there be a third "accident" ? I hope not.

[arftist]

By the way, you can blow up a battery with welding current. I can't explain how this happened, but with the welder on, I connected the ground clamp. The stinger must have been in contact with the body or the bed of the truck. As I walked arround the front of the truck, with the hood open, the battery exploded in my face. But for the grace of God, I suffered no permanent damage. I dove face first into a snow bank, and by the time I was standing up, a mechanic grabbed me, and got my face under running water inside the service station. I will never weld on a vehicle with the battery connected no matter how many times you say that nothing will happen. Been there, done that.

[evfreek]

I am not sure if this has anything to do with this thread, but I have found that HF really seems to get around. I have an add-on HF box, and when I turn it on, the GFI to the workbench outlet always trips. It will trip the GFI even when it is not plugged into the GFI outlet. Even if it is plugged into a circuit on another breaker, it will trip the GFI. But, if I unplug all power cords from the GFI outlet, it will not trip the GFI. I added an industrial strength line filter inside the HF box, and the results are exactly the same. That means that the HF is not getting out through the power line, and it is not radiating from the HF box line cord. I then tried keeping the welding leads closer together, and there is more power in the HF spark, but still, it trips the GFI if anything is plugged in. Also, any lights on flexible power cords (not in conduit), flash when the HF is on, regardless of circuit that they are plugged into.

This indicates that the HF is behaving like a radio wave, and the AC impedance to ground of the lighting circuits is much smaller than the DC impedance. The HF will even make a halogen lamp (big) flash. The reason for this is that the HF box is not a simple transformer. It is more like a tesla coil, and the HF bursts are in the range of several amps at thousands of volts. This is what makes them so damaging to electronics. If they make a large halogen floodlight flash, which is plugged into a different socket, they are pretty potent.