? for ya Sparky

[Gary Abbey]

When welding on a completed race car with a MSD ign. Should you still disconnect the ign.,battery,or just shut the main power switch off. Thanks

[Sparky]

Gary,
This is a great question!
I have some examples of what can happen when you don't fully disconnect a car electrically, prior to Welding on a car.

Welding on a car creates a lot of problems electrically.
I try to make it a habit to disconnect everything.

1.) Power & Ground at the Batteries. (Manny Buginga lost both of his Batteries form welding with them connected)

2.) Ignition & EFI Boxes, Remove them form the car!
Granted I have only lost one Digital 7 Ignition box in all the years I been doing this, this was because the car was welded on with the Digital 7 hooked up and in the Car. To reduce any type of weirdness that may happen while welding on the Car, do yourself a favor and save a lot of headaches. Remove it form the car and when your done welding, you can rest assure that when you put the Ignition back in the Car, more times then not, it will functiuon without any problems.

3.) Fan, Water Pump, Fuel Pump and any other accessories. Please disconnect these Items as well. If your Car does not support some type of central Grounding point, then I highly recommend disconnecting these items.

4.) Data Loggers, Remove them form the Car!
This is not only an expensive piece of equipment, but also a very sensitive piece when it comes to voltage spikes.

Ground is the open door and the insult to injury when welding on a car. Although welding on a car might seem simple enough, but when you consider what type of Amperage you are sending into the weld, is basically what your charging the grounding point of the car with (where the Clamp on the Welder meets the car, usually chassis). This is where the problems come into the electrical system. because anything grounded to the Car is victim of getting spiked with amperage.

Thank you for the great question and I hope this helps.
Sparky

[LTLHOMER]

Gary,
This is a great question!
I have some examples of what can happen when you don't fully disconnect a car electrically, prior to Welding on a car.

Welding on a car creates a lot of problems electrically.
I try to make it a habit to disconnect everything.

1.) Power & Ground at the Batteries. (Manny Buginga lost both of his Batteries form welding with them connected)

2.) Ignition & EFI Boxes, Remove them form the car!
Granted I have only lost one Digital 7 Ignition box in all the years I been doing this, this was because the car was welded on with the Digital 7 hooked up and in the Car. To reduce any type of weirdness that may happen while welding on the Car, do yourself a favor and save a lot of headaches. Remove it form the car and when your done welding, you can rest assure that when you put the Ignition back in the Car, more times then not, it will functiuon without any problems.

3.) Fan, Water Pump, Fuel Pump and any other accessories. Please disconnect these Items as well. If your Car does not support some type of central Grounding point, then I highly recommend disconnecting these items.

4.) Data Loggers, Remove them form the Car!
This is not only an expensive piece of equipment, but also a very sensitive piece when it comes to voltage spikes.

Ground is the open door and the insult to injury when welding on a car. Although welding on a car might seem simple enough, but when you consider what type of Amperage you are sending into the weld, is basically what your charging the grounding point of the car with (where the Clamp on the Welder meets the car, usually chassis). This is where the problems come into the electrical system. because anything grounded to the Car is victim of getting spiked with amperage.

Thank you for the great question and I hope this helps.
Sparky

I don't understand the theory behind disconnecting things when welding on the car...how can power get into all of these devices? They would simply be open circuits and the electricity would flow from where you are welding to the ground on the welder and that's it...I had a bunch of stuff welded in my car over the past few months with everything hooked up (well I had the battery disconnect to the 'off' position) and the car is 100% fine and has been fine since.

I too have heard stories of stuff being killed but I would think that would be a result from someone accidentally hitting a power line or something and then sending that power to devices that can't hand that kind of amperage...I mean if there's an open circuit, it would only get electricity if the resistance from the air (between where the power is flowing and a potential power line of some sort) is smaller than the resistance to the ground on the welder...I mean if none of your wires are bare and touching a part of the car where electricity is flowing, I don't see how anything can happen and I think that's why 'some' people have problems while 'others' don't. It's simply a problem with their wiring and not the process itself...I'm sure it's not too had to disconnect everything but I've not done that yet and everything is fine so it's hard to argue with that...

I guess I just want to know the theory behind the problem...or is it just one of those things that we hear about but never see or have explanation for?

[Gary Abbey]

My brother in law did some welding on his car with only the master switch off. After that it had a miss at high rpm 5000 or above. Hes only running a 6al with the pro billet dist. I checked everything i could think of and every time i put the timming light on it and started to bring the rpm up it would jump all the way over to 50 and somtimes 60 deg. advanced no matter where we set the dist. at. I told him i think that welding on the car i think afected the ign.box,well he went and bought both a new 6al box and dist. and the miss in gone. I was just wondring if you ever ran into a problum like that.THANKS for your time Sparky

[Gary Abbey]

LTLHomer, a number of years back i was welding up my exhust system on my truck (1986),when i lifted my sheild the entire speedometer cable was CHERRY RED! Thats when i learned about how power when welding on a car will travel. The battery cable POS only was disconnected. What a mess.

[LTLHOMER]

LTLHomer, a number of years back i was welding up my exhust system on my truck (1986),when i lifted my sheild the entire speedometer cable was CHERRY RED! Thats when i learned about how power when welding on a car will travel. The battery cable POS only was disconnected. What a mess.

Speedometer cable might make sense since it would be metal to metal with the tranny linkage (and linkage to tranny and tranny to chassi) and then metal to metal where it connects to the shifter which is also connected to the chassis, so you would probably get current through it...and I can see why on some cars it might make a difference, but on a car with a master-shutoff (where it actually shuts off everything), I don't see how a complete circuit would be made to allow the electricity to travel through them and mess something up unless you had wires that were worn down and exposed to the chassis (the ground in this case) somehow...

Chances are the MSD box (aka may self-destruct box) died on its own...that's just what MSD boxes do...and then they look for someone to blame.

I guess I'll take everything off next time but I would really just like to hear about how exactly a problem can result from that...if it happened everytime someone welded, there would be some kind of explanation but the fact that is only happens in rare circumstances seems to suggest that the problem might lie elsewhere but the easiest thing to point the finger at would be the welding deal...

[Sparky]

LtlHolmer,
When you weld on a car you have a clamp attached to the chassis. The Arc of a Tig welder is created when Positive and Negative meet. This clamp can be either Negative or Positive depending how the welder is set-up: DC Electrode negative or DC Electrode Positive.
Being that most Rcaecars use Chassis as Ground, you send current through the Ground side of components. Even though you have the Battery disconnected or Master disconnected shut off, problems can still arise.
An example:
If you weld on a car with the Battery connected, you then send all the amperage you are welding with into the Battery. The amperage flows through both sides Positive and Negative. If this amperage didn’t travel through the car and it didn’t ruin the Battery, then you wouldn’t have to disconnect or remove the Battery. This should be proof enough that in fact Welder Amperage does travel through the whole car including the electrical system.

You ask, “If the Battery is disconnected how would this effect components, because this leaves the circuits open”? Not necessarily,
Electricity will always follow the least path of resistance.
For example: You’re welding DC Electrode Negative, common for Roll Cage work.
Your working with about 25 to 30 Amps, the clamp is the positive side and the Electrode is negative, the arc starts when the two meet, but in the mean time, that clamp is attached to the chassis and the grounds are attached to the chassis. It would be nice to think that with the Clamp attached and you striking an Arc that the amperage is flowing from the Clamp through the chassis to the Electrode. But it isn’t. That amperage is traveling through the Clamp, through the Chassis and through the electrical system, it is going through everything. It could travel through everything in the car, switch panel, relays and components, whatever. All it takes is for this amperage to make its way into both the Positive side and the Negative side of the electrical system and problems begin, just like the Battery example above.

A typical Digital 7 MSD Ignition only pulls 1 amp for every 1000 RPMs. If you spike that Ignition with the above mentioned amperage, through the Ground side, through the windings in the transformer and back out the Positive side of the main power of the Ignition, now the amperage has made its way into the positive side of the electrical system, along with sending that same current through the Trans Brake ground side, through the coil of the Trans Brake, into the Positive side of the Trans Brake, into the 2 Step wire and back into the Ignition, then through the Ground in the Tach, through the Tach into the Tach Wire and back to the Ignition. Then there is the Line Loc, through the Ground side of the Line Loc, through the Coil of the Line Loc, into the Positive side of the Line Loc, into the Burnout wire that leads back to the Ignition. Oh and lets not forget the N20, through the Ground side of the N20 Solenoid, through the coil, into the Positive side of the Solenoid, into the retard wire that leads back to the ignition.
That’s 5 different avenues the Ignition has just been hit with Welder Amperage, do you really expect this Ignition to work as it did prior to you welding on the car?

Sparky

[Mark Nealen]

Hey
can you tell me if it is possible to somehow have reversed the polarity of a electric fan? maybe caused by the welding. I had a problem with a electric fan a while back. When I ran the red wire to + and black to - It ran backwards and would run forward the other way. And it used to run the other way! When wired red to red it also burned up two MSD 6 al ignitions? I never found out what the real cause of this was and would really like to know. Thanks Mark

[LTLHOMER]

LtlHolmer,
When you weld on a car you have a clamp attached to the chassis. The Arc of a Tig welder is created when Positive and Negative meet. This clamp can be either Negative or Positive depending how the welder is set-up: DC Electrode negative or DC Electrode Positive.
Being that most Rcaecars use Chassis as Ground, you send current through the Ground side of components. Even though you have the Battery disconnected or Master disconnected shut off, problems can still arise.
An example:
If you weld on a car with the Battery connected, you then send all the amperage you are welding with into the Battery. The amperage flows through both sides Positive and Negative. If this amperage didn’t travel through the car and it didn’t ruin the Battery, then you wouldn’t have to disconnect or remove the Battery. This should be proof enough that in fact Welder Amperage does travel through the whole car including the electrical system.

You ask, “If the Battery is disconnected how would this effect components, because this leaves the circuits open”? Not necessarily,
Electricity will always follow the least path of resistance.
For example: You’re welding DC Electrode Negative, common for Roll Cage work.
Your working with about 25 to 30 Amps, the clamp is the positive side and the Electrode is negative, the arc starts when the two meet, but in the mean time, that clamp is attached to the chassis and the grounds are attached to the chassis. It would be nice to think that with the Clamp attached and you striking an Arc that the amperage is flowing from the Clamp through the chassis to the Electrode. But it isn’t. That amperage is traveling through the Clamp, through the Chassis and through the electrical system, it is going through everything. It could travel through everything in the car, switch panel, relays and components, whatever. All it takes is for this amperage to make its way into both the Positive side and the Negative side of the electrical system and problems begin, just like the Battery example above.

A typical Digital 7 MSD Ignition only pulls 1 amp for every 1000 RPMs. If you spike that Ignition with the above mentioned amperage, through the Ground side, through the windings in the transformer and back out the Positive side of the main power of the Ignition, now the amperage has made its way into the positive side of the electrical system, along with sending that same current through the Trans Brake ground side, through the coil of the Trans Brake, into the Positive side of the Trans Brake, into the 2 Step wire and back into the Ignition, then through the Ground in the Tach, through the Tach into the Tach Wire and back to the Ignition. Then there is the Line Loc, through the Ground side of the Line Loc, through the Coil of the Line Loc, into the Positive side of the Line Loc, into the Burnout wire that leads back to the Ignition. Oh and lets not forget the N20, through the Ground side of the N20 Solenoid, through the coil, into the Positive side of the Solenoid, into the retard wire that leads back to the ignition.
That’s 5 different avenues the Ignition has just been hit with Welder Amperage, do you really expect this Ignition to work as it did prior to you welding on the car?

Sparky

Electricity travels the path of least resistance...this I know...but an open circuit has infinite resistance...let's say it goes through my linelock ground, and then into the switch wire...which goes into fuse box (which would blow at 5amps but let's pretend it's not fused), it then goes to the positive distribution block, and then to the cutoff switch which is in the off position...and then it has nowhere to go...that's not a complete circuit back to the ground so it wouldn't even attempt to take that path...I mean even the scenario of it going into the ignition, it still needs a place to go out so it would have to arc inside the box for something like that to happen I would speculate...every positive wire in my car can be disconnected by the cutoff switch, and with it disconnected, there is no complete circuit unless a wire has worn through and is rubbing the chassis and even then it would have to be less resistance than the path to the ground of the welder...because the amperage it would get would be inversely proportional the resistance of its own circuit...

I have almost everything on my car fused, and after the welding, all my fuses/circuit breakers (most being 5-15 amps) were perfectly fine indicating the electricity did not travel through any of these things...like I said...I buy into that fact that if a complete circuit exists, then problems can arise...but in my situation, it had nowhere to go and therefore did no harm. Will I unplug it next time? Of course because what if one of my positive wires rubs metal and contacts the chassis enough to create a short circuit...but to say it's automatically going to cause problems seems a little misleading...everything works exactly as it did before, none of my fuses were fried (there's 15 in the car), and nothing has changed except my seat brackets are welded to the car...lol

[craggar]

I agree it's a good habit to diconnect everything but I also agree with LTLHOMER. When I was in my apprenticeship for welding the question came up about welding on cars and we were told to diconnect the battery and put the ground clamp as close to where we were welding as possible. I have done a fair bit of welding on my cars using this practice with no issues yet.

[Six_Shooter]

Electricity travels the path of least resistance...this I know...but an open circuit has infinite resistance...let's say it goes through my linelock ground, and then into the switch wire...which goes into fuse box (which would blow at 5amps but let's pretend it's not fused), it then goes to the positive distribution block, and then to the cutoff switch which is in the off position...and then it has nowhere to go...that's not a complete circuit back to the ground so it wouldn't even attempt to take that path...I mean even the scenario of it going into the ignition, it still needs a place to go out so it would have to arc inside the box for something like that to happen I would speculate...every positive wire in my car can be disconnected by the cutoff switch, and with it disconnected, there is no complete circuit unless a wire has worn through and is rubbing the chassis and even then it would have to be less resistance than the path to the ground of the welder...because the amperage it would get would be inversely proportional the resistance of its own circuit...

I have almost everything on my car fused, and after the welding, all my fuses/circuit breakers (most being 5-15 amps) were perfectly fine indicating the electricity did not travel through any of these things...like I said...I buy into that fact that if a complete circuit exists, then problems can arise...but in my situation, it had nowhere to go and therefore did no harm. Will I unplug it next time? Of course because what if one of my positive wires rubs metal and contacts the chassis enough to create a short circuit...but to say it's automatically going to cause problems seems a little misleading...everything works exactly as it did before, none of my fuses were fried (there's 15 in the car), and nothing has changed except my seat brackets are welded to the car...lol

QFT! (Quoted For Truth)

There is NO way that welding on a car will cause ANY damage to the electrical system, PROVIDED, the ground strap (for the welder) is connected solidly. The path for the weld is:
Welder > cable > chassis > torch > cable > welder.

NOT:

Welder > cable > Chassis > then randomly travel through some other component > torch > cable > welder.

The welder does NOT become a power supply for the car, which it would have to to cause any damage, it is actually a seperate power supply, that shares a common component for conducting electricity, the chassis, but again, it's from a seperate source.

To put it another way:
Ever hear of the myth that theives can get around security systems simply by attaching a battery to the chassis of the vehicle?

Go ahead, try it, all you will do is short out that battery and cause a bunch of smoke to pour off the cables, damgging only the second battery, and maybe a couple melted spots on the vehcile chassis where the cables were attached to, oh wait this seems familiar, sounds a lot like welding. ;)

To further illistrate the point that welding will not damage the vehicle electrical system and components, start the vehicle and let it run WHILE you weld on it, I do this on a semi regular basis, usually to seal up a patch job on an exhaust system.

If there would be any damage to occur, the car should shut off immediatly as the torch button was pulled. ;)

[RRRAAAYYY2]

First I have to compliment you guys. We do electrical seminars for licensed mechanics all the time, and so far this conversation is more intelligent than what happens at most our seminars.

Six Shooter,
My point is probably best explained with an illustration. For years we have warned our customers that boosting a vehicle can and will caused damage. Everytime the cables are connected or disconnected there is a chance of blowing diodes out of the alternator, any noise suppression device, and any computer containing an IC chip.
I have a friend that used to drive for CAA. Everytime we got together we would argue about this. His point was he had boosted over a 1000 cars and never had a problem. My answer was always two fold. First he didn't know how many cars he may of damaged, as he could always say the bad alternator was the cause of the dead battery, whether it originally was or not. Second was he was right, he may have done it 1000 times without doing any damage, but 1001,1002,1003 all might be the times he will blow stuff up.
Last year we got together and he walks up to with chin on his chest. His battery went bad and he had to get another CAA truck to boost him. When they took his booster cables off his alternator light came on, and the other truck died. He had blown the diodes out of his alternator, and fried the computer in the other truck.

Another guy a couple of years ago took three computers out of his 6 month old truck when he disconnected the booster cables. So sometimes it is not just one and your done.

I can think of at least 10 stories like this, and we have seen on average probably 1 or 2 alternators a week for the last 15 years that where damaged by welding, removing of the positive or negative cable while running, lightning, or boosting.

I would think you have only been very lucky so far. It is a definite advantage that the exhuast systems in most modern cars are hung off rubber grommets. But I can say for certain, you are rolling the dice each and every time you weld with everything connected. The potential for you to destroy every computer in the car, along with the alternator, and possibly even the battery is very high.

This is a hard and true fact.

How to prevent this is somewhat debatable, actually it is more to what lenghts you need to go to to prevent that can be questioned. Some newer welders have clamps that guarantee they will prevent this. Some of my customers agreed with them, for a while anyway. They are better than older units, but still not 100% full proof.

In a race car disconnecting the kill switch should do it. Notice I used the word should, and not the word would. If you are in a hurry, I would consider this the very least thing you can do before welding.

Disconnecting the battery is a far better way to do things. This almost guarantees, about 99.9%, that you will not damage anything.

But as Sparky first outlined, the only 100% for sure way to guarantee an item's safety is to completly disconnected it from both power and ground. When the trigger is pulled, everything in the vehicle has the potential to make a circuit. All any of them needs is for it to have a small leak and for it to be the path of least resistance. And since almost all sensitive electronics have spike suppression protection built in, they all have small leaks. So really they only need then to become the path of least resistance and you will be buying a new one.

Electricity is funny that way. The path of least resistance is seldomn the most logical path for it to take. (I may get corrected on what i am about to say, but I will say it anyway) Electricity travels very quickly, and does not adjust its path easily. Pretend it was a car driving down the highway really fast. It comes upon a truck stalled in its lane. It cannot swerve and just go around the truck. It hits it and goes off on a bit of an angle, then refocuses itself on the path of least resistance all over again. But now it is starting from say 8 lanes over. Now there might be quicker route to take from this new location. But it might run into another truck and angle off 10 more lanes, and then again, and again. Next thing you know you are in New Jersey instead of Long Island. (I hope that made just a little sense, LOL).

When you clamp a car, the path of least resistance should be directly from torch to the clamp, or vis a versa. But as your surfaces get hot, their resistance increases, and that can lead to the electricty wandering, which can lead to potential problems. With the battery out of the equation, the potential is low, but with your devices out of the equation, the potential no longer exists.

So it all depends on how much time you have and how much money you have to gamble with. The last time I had my truck welded I spent 2 hours disconnecting my amps, and still made them disconnect my batteries as well. Since i am pretty lazy, you can rest assured I didn't do it because I was bored.

Hope this clears things up a bit.

[RRRAAAYYY2]

LTLHOMER,
I understand where you are coming from. I would like to correct one thing though. In your last post above you stated an open circuit has infinite resistance. It may seem like that, but I have to disagree.
Consider a spark plug for instance. It is basically an open circuit. But with enough voltage it becomes a closed circuit.
Air is actually a very good insulator, as it is full of resistance (when it is pure). If you consider that the clouds above us are seperated from the ground below us by air, it is a very large open circuit. But when enough voltage is built up, the electricity has the power to overcome this resistance.
I know these are both very high voltage situations. But if you consider in order for you to see electricity (i.e. a spark) it has to be somewhere over 20,000volts (forget exact figure). So even that little blue spark we see when connecting/disconnected battery cables has huge potential.

[RRRAAAYYY2]

Hey
can you tell me if it is possible to somehow have reversed the polarity of a electric fan? maybe caused by the welding. I had a problem with a electric fan a while back. When I ran the red wire to + and black to - It ran backwards and would run forward the other way. And it used to run the other way! When wired red to red it also burned up two MSD 6 al ignitions? I never found out what the real cause of this was and would really like to know. Thanks Mark
Mark,
I forget the exact explanation of how, and can check in about ten days when someone comes back from vaction, but yes it is possible. Your fan is likely a permanent magnet motor and had the permanent mangnets polarity reversed. if it is possible to do, if you turn the field case assemble with the magnets in it around, it will go back to normal. Now this is going to bug me all weekend, it has happened before, but is pretty rare.

[RRRAAAYYY2]

A couple of you have mentioned blown MSD boxes. If they worked the day before you welded, and not the day after, I would definitely chaulk it up to welding.

Another common cause is the brushes and diodes of the alternator. Voltage spikes have two common sources. When large loads are switched on and off, things like your starter or NOS solenoids, they create a voltage spike. It happens very quickly, and very briefly. So much so that the sample rate of most data loggers won't catch it. It also takes the shortest path to ground of the battery, so sometimes the whole system doesn't see it. (battery's secondary purpose is to absorb these spikes).
Your alternator is a fairly constant source for spikes. As the brushes ride on the slip ring, they sometimes bounce, and when this happens they create a small spike. how large it is depends on what alternator you are running. If it is an old style Delco or Ford, it can be upto 200 volts. This is why we recommend alternators with the newer avalanche diodes, as they supress spikes over 32 volts. MSD and other computerized equipment can handle 32 volts for fractions of a second. 200 volts they can't.

MSD and other manufacturers build protections into the equipment, but they are not fail safes. Keep pounding them with spikes and they eventually will lose the fight. I have seen lots of cars equipped with older alternators have premature MSD failures, and none so far with avalanche diode equipped alternators.

There are two ways to avoid this. One is to use an alternator that has avalanche diodes in its rectifier. The second is to wire the alternator directly to the battery, with no power take offs along the way. The second way is a no-no according to IHRA and NHRA rule books. Though I have had conversations with IHRA national tech director, and he said they would allow it. There are several advantages of wiring directly. First and foremost, it is the only way to instantly shut the car down using a kill switch. It doesn't blow your alternator up when you use the kill switch either. It also gives your system a cleaner DC pattern, as the battery flattens the pattern out.
Big disadvantage is it leaves two wires live. One from the battery to kill switch, and one from the battery to the alternator. If you use a big fuse on the alternator line, it will pop if the line is shorted. Another disadvantage is you need a pretty big wire running front to back, and this is $$$ and weight.

[Six_Shooter]

Ray You bring up some good points, like the open circuit as compared to a spark plug, but then that brings me to my point that NO ONE can explain. ;)

If that's the case, then disconnecting the battery will do NOTHING, in fact, possibly making it worse by the logic you bring up. ;) The battery terminals that we disconnect are usually closer to the chassis then they would have been if they were connected to the battery, causing that air gap to become smaller, making the "resistance" less and easier for the spark to jump the gap, so now I guess we need to put a rubber sleeve over those terminals. *shrug*

Now, to bring up another point, if the battery needs to be disconnected to protect it from the welding, then EVERY SINGLE ELECTRICAL component in the vehcile would also have to be disconnected, or more probable, REMOVED from the vehicle to weld something on that vehicle, otherwise imminent damage will occur, which we all KNOW is not the case.

The battery can also act like a spike suppressor, oh wait it does that in normal opperation. ;), filtering out ripples and spikes generated by the alternator AND other electrical components when they are switched on and off. Granted while these spikes are sometimes several thousand volts, they are at a lower amperage than welding., but again, I've never seen a electrical current flow get bored of the path it was already on, and deviate from that shortest path, NEVER. The only time the path would change is IF the path it was on, was somehow interupted, while still having another path imedialty available, but again, that path would have to be THROUGH the component that you are worried about.

Maybe we shuld mention RF, and inductive nature of electrical components. Which is a MORE likely cause of damage while welding than current from the welder itself. It is for this reason that if I am welding near an ECM, or other electrical component, I usually remove it or move it away, I try and stay a few feet from things like this.

I guess a better test would be to leave a vehicle connected and weld on the vehcile, while testing for voltage spikes at components, caused by the current transfer on the chassis, through the use of DMMs and O-scopes.

Oh and Ray, check how isolated those exhaust systems are, in most cases not very, everyone seems to forget about the connetion at the manifold/header. ;)
besides that was just one example, and about the only one I could think of where I'd want the car running while welding. :lol:

[RRRAAAYYY2]

Ah, I will try again. disconnecting the battery does do something. It puts air inbetween the negative post of the battery and the ground path (the cable). With it disconnected the current now has to jump that space. (Air is a super huge insulator). Which is a lot harder to do than for it to find an alternative way back to the clamp of the welder.

With the battery connected, it is different. It means there is very little resistance in the ground path of the battery. Which means the current might find it an easier path than the path to the clamp. Without the battery you have no alternative other than the clamp and the ground under the car.

About removing all electrical components to stay out of danger. To be 100% safe, the answer is yes. If at any point your current from the welder finds it path to ground through any component on the vehicle, you will eat that component on the spot. With the exception of maybe the starter. Because this has not happened to you yet, does not make it not true. It does not happen on a regular basis as the current has to over come an open circuit, which is difficult, but not impossible.

As for electrical paths. Physics state that electrcity will always take the path of least resistance to ground. Not the shortest path, the path of least resistance. If the path it is on (which would be the one of least resistance) for some reason increases in resistance, i.e. it gets hot from use, and another path with less resistance is available, it will change to the new path.

Having a car running while welding is absolutey crazy, sorry for the phrasing. If the car is running, you have no open circuits, everything is closed. So you offer no protection to anything. think the battery is going to help. Sorry but batteries cannot handle more than about 15.3 volts and 50amps of input. anything more than that and they will boil, too much more than that and they explode.

I hope you don't think I am making this stuff up. This comes from the heads of the Auto Electric Rebuilders Association of Canada, Tech writers for the ERA, and the head of the electrical division of the APRA in the US. Trust me, you are rolling the dice and are going to eventually get burned.

As for RF causing problems, I will have to look that up.

[Sparky]

You won’t have to look it up Ray. I have this article, which I feel is well written and best describes EMI and its subclass RFI. I often use this as a reference.
http://www.narcap.org/Jim-Burrell-April-2003.pdf (http://www.narcap.org/Jim-Burrell-April-2003.pdf)

I don’t think a welder puts off RF but rather EMI.

In talking with a couple of my older mentors in the electrical arena, one of which carries a PhD in Electrical Engineering, the idea of welding on a car while sensitive electrical components are connected, primarily to the ground side of a car, is not something that is recommended and definitely not encouraged by these guys nor anyone else I have researched this with. In fact, everyone I have talked to seems to agree to get the items out of the car and disconnect the grounds.

Sixshooter, you state that you weld on a car while it is running and you also say you do this on a semi regular basis. Although you state that no apparent problems occur while doing this at that time. As Ray points out with Boosting vehicles, in a short time following the boosting incident, something electrically related usually fails.
The same probably does hold true for welding on a car while it is running or while someone didn’t bother to disconnect components and grounds, the insult to injury has been added to the equation and it’s just a matter of time before failure sets in, how long before failure is anybody’s guess, but I will surely bet it isn’t long. All of the OE Automotive Manufactures have welding guidelines within their Service Manuals.

In fact I would challenge you to call MSD, FAST, Accel DFI, EFI Technologies, Mallory, MoTec, Race-Pak, Autometer, PowerMaster, East Coast and ask them what their recommendations are for welding on a car, while their components are installed and hooked up or while the car is running.
These are the people who design and build these products. Ask them, if it fails while welding on the car, will they warranty it.
If a product fails shortly after a car has been welded on, these are the people who are going to be receiving the phone calls, with that being said, wouldn’t it just be best to follow their recommendations prior to welding on the car?
There is no point in hooking up meters and scopes to a vehicle and its components to conduct tests, to investigate the adverse effects of welding on a car.
The manufacture is never going to warranty anything that has been in a car while it was welded on, regardless of what these tests prove.
My close friend with the PHD can explain what the adverse effects and outcome of your tests will be without ever hooking up a scope or a DVOM.

Monty created this section and asked me if I would moderate it. I was excited to become part of something as big as Yellow Bullet has become. With my professional background and resources in the electrical field, I was also encouraged to do my best to provide accurate useful information.
When people come here for help, questions and recommendations, I try to give them something valid. I like to know what I’m talking about before I post. And if I’m not sure, then I research the concern, so that when I do post, I’m providing correct accurate information.
I have done the same with this post and although this topic has been challenged with some good counterpoints, I was trying to provide for Gary the best solution for his question. I have always practiced and will continue to practice removing sensitive items from the car and disconnecting the grounds, prior to welding on them. Why? Because this method has always provided no problem results and in my professional opinion provides the best results. I don’t know how Gary values his money. Maybe he has lots of it and can piss it away on buying new ignition boxes and data loggers, etc and is too lazy to disconnect grounds. But realistically, he is like most people and probably values what he has purchased and would like to keep it in good working order, that’s probably why he came here and asked me what I thought he should do, before he started welding on the car.
Furthermore, is there really that much added work in removing sensitive components from the car and disconnecting grounds, I look at it as a really cheap insurance policy.

Sparky

[Monty Mikho]

Guys excellent posts and questions on both sides. Me being in the machine tool industry we know things get screwed up in circuit boards if welding on a machine with the grounds still hooked up. I have no idea why this happens.. but it does... Rather than me question why I play it safe and disconnect every ground and all 3 phases on a machine before having something welded on it. This is with machines that have a true earth ground. I play it safe because if the machine doesn't power up after we are done welding we have better than a few $100,000 of electronics that are wasted. I have seen machines that have lost memory, burned ground cables, signal cables and blown internal electronics on boards from welding while grounds and/or power were still hooked up. Sometimes things can't be explained on why. But that doesn't mean it doesn't happen..

(I can see Ray all over this one in another section of the board.... Oh boy)

[RRRAAAYYY2]

Sparky,
Thanks for the article. It was a long the lines of what I was thinking. Though I do know of one instance where RF did cause some problems. But it is in an an operating circuit, not one that was open. Kind of funny stroy. I get a call from my local fire department mechanic, and he is in a panic. Which could mean anything, and I have literally had trucks stop at my shop on their way to calls.
Anyway the radio in the cabin of a truck had a push to talk mic, and an automatic mic. The radio would on ocassion turn the automatic mic on. Not usually a problem until one day when the 5 guys in the cabin were trashing their superior really, really badly. Everyone in the station got to hear them, including their superior and anyone on a scanner. The manufacturer of the radio couldn't figure out what was wrong, so they called us. We suggested putting a noise supression diode in the power supply to the radio, and all was good after that.

To add to your list of companies that have warranty policies that do not cover welding on a vehicle, you can include every Alternator manufacturer or remanufacturer or rebuilder that I know of, which is probably close to 90% of everyone in the world.

As for your moderating skills, I think you are doing an excellent job. I check in here every now and then, and your replies are excellent.

Six Shooter,
I hope we don't sound like we are banging on you to hard. I am well aware you have doing things a certain way, and have no apparent problems. So it makes it difficult to swallow what we are saying. But in the long run you can either believe us now, or later. But at some time it is going to happen. I have always found it is cheaper to learn from others mistakes than to do it on my own.

Monty,
LOL. You haven't heard me say that yet have ya?

[Six_Shooter]

EMI, was what I was trying to think of, not RF, it wasn't coming to me earlier. :)

Ray, you know you and I will never agree on many points, and I will fianly reveal the reason why.....

I have seen more failures of componets, less reliability and less overall performance, in many things in the many arenas we disagree on, and you know I'm talking about more than just welding on a car. ;) But I guess that's where our differening experiances makes each of us more steadfast in our devotion to our own techniques.

I respect everyones opinions here, especially those with more experiance than myself, but through experiance and listening to others, I have formed my own ways and opinons on how I do things.

I'm also quite sure that any electrical failure after welding on a car, would not be a direct result of that welding, again, go back to my example of connecting a battery to the frame, we should all know, that all that is going to happen is a melt down of that shorted external battery circuit, and effect nothing mounted and connected to the car.

Also I have to ask, that anybody who welds on a late model car, meaning '95+ do you remove the PCM, BCM, Radio, Gauge Cluster, Heater Controls, AND any other component that is more than just a simple light circuit? If not, Why not? That is what you are saying to do after all.

The way I see it, is that regardless of the battery being connected or not, it will not change the survival potential of any electrical component in the vehicle, according to what is being said in this thread. There are MANY circuits still connected, even with the battery taken out of the equasion, a closed circuit does not always need to have a battery in the loop, but a circuit that retuns on itself, such as MAP sensors, the Ground and reference both connect to the ECM/PCM, as one example. So by what is being said here, just the fact that the PCM ground is attached to the chassis of the car (usually through the engine block, to the chassis ground), then it should be instantly fried.

I bet if you looked a little more indepth to the failures due to welding and jump starting, you'd probably find a previous weak link, that would have failed in a short time anyway.

BTW, I'm not saying NOT to disconnect any components while welding, far from it, I'm just saying that from everything I've seen, read about, watched, or performed myself, it hasn't made a hill of beans difference.

BTW, go ahead pick on me, I can take it. ;) :)

[RRRAAAYYY2]

You are talking about your experience as one shop. I am talking about the experience of 10,000 shops, dealing with 100,000's of shops like yours. You can choose to agree with me or not, it will still not change the fact that in almost all likely hood I will have an alternator in my shop next week that was working fine one minute, then ...
Had someone remove a battery cable while it was running (most common) or someone welded the vehicle ...
And now the prevoiusly fine working alternator is missing one diode. The diode is not blown, it is not leaking, it and part of the rectifier bridge that housed it are missing, completely gone.
I never had one last week, so I am due this week.

About the closed circuits in the system, they may be there (don't think they are but....) but they are connected to an open circuit and need that circuit to close before than see exposure. Your computers are not constantly working while the ignition is off.

I don't know how to better explain this to you. I apologize for not being able to give you the information to change your mind. But as I tried to say earlier, this is not something I made up on my own. My industry's leaders, its guru's and everyone I know in it will all agree with what has been said. We all have personal experience with it, so I don't know what else to say.

[Rick_R]

welding does put EMI, the older the welder the higher the EMI in my experience. There used to be an "antique" welder in my shop that was used in production, It was taken out of service by the FAA, it had so much EMI it was setting off alarms in overflying airplanes.:shock: