Questions about welding on a vehicle

[fillethead]

Hey all,
What precautions should be taken when welding on a vehicle (car, motorcycle, ...) to protect the vehicles electronics (computer, sound system, ...) ?

I have heard keeping the ground clamp positioned as close (circuit path) as possible to the weld zone is a smart thing to do. What about disconnecting the battery?

Fillethead

[DLite]

You got it.

Do both (close ground and discconect the battery) and you're good.

[ironmangq]

I would at least diconnect the battery to be safe, I have welded on vehicles plenty of times without doing anything and have never had any real problems (I may have killed a voltage regulator once, but im still not sure it was the welding). The fact is, everything in your vehicle is still connected to ground and anything else it is wired to, by removing the battery all your doing is removing power that is usually already switched off to the electronics by the relays under the hood, so all your really doing is taking power away from the distribution box. Grounds are still vulnerable to being burned out if exposed to welding current provided it provides a better path to ground than whatever your welding on.
So dont go doing body work and welding on door skins while grounding to the frame on the other side of the vehicle. Always ground to the piece you are welding on if possible.

[Rbeckett]

Smart money sez, disconect the battery and do what you need to do. I have never had an issue but if something does happen can you afford that 3 thousand dollar control unit and a rental car till it gets here? When I worked fro Firestone and Goodyear the policy was disconect....Period. Some folks do, some dont it's really your call, but think with your wallet before you make a huge mistake and bankrupt yourself in the meantime. Just my .02 FWIW. Did it for 35 years so I got a clue.
Bob

[Gamble]

Be sure to check both sides of what you are welding too. You make sure you are far away from fuel lines and such.

[farmersamm]

All manufacturers recommend disconnecting the harness to the ECU in addition to disconnecting the battery. You can have voltage enter the unit thru the ground or power leads even with a disconnected battery. It doesn't take much voltage to fry a puter.

This said..........A lot of people weld on their vehicles without the above precautions.

Personally, I'd go the safe route

Even though the work clamp is close to the welding area the entire chassis is energized when you weld, it's just looking for a return path, or a path to ground. Most of the time it'll return thru the work lead, but....................

[G-son]

The magnetic field caused by the welding current will induce (correct word?) a voltage in any metal near it, basically creating a primitive transformer. A wiring harness close to anything related to the welding (such as the ground wire just passing near by) can pick up enough voltage to fry whatever electronics connected to that harness.

In other words: Unplug everything sensitive you don't want to risk frying, or keep well clear of anything connected to the electrical system in the car and take the risk. Few customers will be prepared to pay for the time involved in unplugging everything that should be unplugged...

[Timster2]

Disconnect the battery, both sides. If you are welding in the area of the computer disconnect it as well. Remember there are several computers in the car/truck. Door modules trunk modules, alarm, engine control, fuel system, so be real careful. If at all possible take the part to the bench and weld it. Moving wiring harnesses away from heat as well as electromagnetic fields is a must. I once worked on a Jeep that had some welding on the door. A week later the headlights would flash and horn honk in the middle of the night for no reason. Turned out the welder did not put his ground on the door, he had ground clamp on the body, and fried the door computer module. Not enough ground through the door hinges!

If you disconnect computers make sure you practice good personal static control. It is just too easy to fry a computer. Remember failure is not always immediate.