I know exhaust shops often weld on
customer cars without apparent steps
to isolate the electronics.

However, I have some future plans for
work on my '89 that entails arc/mig/tig
welding on the frame and I would like to
take precautions so that the electrical stuff
all still works when I am through.

Please jump in with any recommendations
about how to protect items like the ECU,
digital dash, ABS unit and etc.

.

 

Unhook the battery cables.

 

I just unhook the battery. Never had a problem. But if you wanted just unhook what your afraid of hurting.

 

Wrap or bolt a heavy chain to the frame and let the chain lay on the floor...Instant ground...
-Jeb

 

I guess if it were me, and i was concerned with damaging the ECM (or anything else for that matter) I would simply take the extra few seconds to unplug the electronic part. Cheap insurance.

 

Chain on the floor will do nothing, it isn't static electricity that you need protection for. Also, unplugging the ECM won't help because you would have to unplug every electrical device, which isn't practical. Remove the negative battery cable (because a wrench on this terminal can touch ground without fireworks!).
Welding current across the frame causes a voltage across the frame which is in series with the battery to the loads that are always on like the clock , ECM, etc. With the battery disconnected the voltage across the frame is no longer connected through the battery to the loads.

 

jfb, i was just referring to unplugging the ECM not to damage IT. This would obviously work. As for everything else, i agree whole-heartedly. ANYTHING left plugged in will still be able to suffer damage through ground. Sorry if my (so called...lol) help wasn't clear enough, sometimes i type faster than i think

 

Well now you are correct, the ECM would be protected and of course it would be easiest to protect everything by disconnecting a battery connection. Maybe all you need is to take a speed typing class!

 

Some shops buy a surge protector that you connect to the negative and positive terminals on the battery, they don't even disconnect the negative terminal from the battery..... just my 2c.

 

There is no component that you can put across the battery terminals to protect damage from welding with the battery connected. Disconnect the battery!

 

For what it's worth, a lot of the manuals I deal with recommend unhooking both battery cables. Unplugging anything else, pulling ECM fuses etc., certainly isn't going to hurt anything either.

 

Hey ! Listen up ! I was a certified welder in my younger years ! and not only can you damage the electrical stuff , but with any type of arc welding , mig , tig ,stick , you can damage the engine ! the problem is that the arc is looking for a way to complete the circuit , either straight or reverse polarity and it can arc in the bearings , causing scars between them and the crankshaft . this can lead to bearing failure , normally a spun bearing ! Try to keep the ground lead as close as you can to what your welding !

 

I can see that, electricity can do some strange things. I've always heard to keep the ground close. Thanks for the tip!

 

As most of you guys know I was (and now part-time) a electrical engineer specializing in process controls in pulp and paper mills. As a consultant to this industry, I was often hired on to supervise installation and start up of large control systems and specialized machine drives. All of which is very sensitive in one respect or another.

When I am on a job overseeing construction. One of my mandates was that any welding that was done near any of my equipment had to be done with their ground leads as close to their work as possible. Grounding to any electrical PE grounds was strictly forbidden, as was grounding via laying peices of pipe together to form a ground path, grounding to my conduits or anything just plain stupid. Most of this stuff is common sense to any journeyman welder.

I don't claim to be an expert welder by any means, but I can hold my own with most any backyard Joes that can weld. I have never blown or disrupted any electrical device in any vehicle I have worked on by weldling. As long as you use your ground clamp correctly and as close to the work where the welding is to be done you won't have any problems. The current will only flow between the torch or electrode and the ground clamp. Do something stupid like putting an ECM between the two and you will have problems.

For instance if you clamp your ground lead on the tranny and weld on the rear end, you may risk loosing a driveline yoke bushing because current may flow from the tranny housing throught the bushing through the driveling to the rear end. Or you may waste a pinion bearing or a carrier bearing if the current flows through those bearings.

If you let the smoke out of the device it will no longer work as designed And beleive me I have seen a lot of smoke that leaked out of a lot of high dollar equipment due to something dumb.

 

Thanks to everyone for your input. Here's
a summary of what I believe you've told me.

- disconnect neg. and pos. conductors to battery
- establish welding ground immediately adjacent
to weld.
- ensure that good metal-to-metal contact occurs
at ground clamp
- optionally remove fuses and disconnect any
equipment of particular concern

The peace of mind this brings is much appreciated.

.