Ground Loop

[AZ73]

Per NTSQD's excellent suggestion to start this thread, I ran a ground loop around the entire vehicle that ends at the battery ground to help deal with Bronco ground issues. Then I grounded everything to the body and/or frame AND the ground loop. Plus ground straps the the engine/frame/Body. But now someone told me the grounds from one component will become a positive to another because all the grounds are tied together. Is that really an issue and if so, any suggestions?

 

[73azbronco]

no. Unless you start playing with a PWM type electrical system, having a ground all around is not a bad thing. But, I only run a ground wire to rear of frame, engine to frame, battery to frame and front clip to battery. Also, engine to body, body to frame. Oh, one more inside dash area, and of course factory wire running up to wiper.
If you think about it, the body is a big circle so is the frame.

PWM is a nwere setup using a coded signal that can get messed up if there are loops.

 

[ntsqd]

The whole grounding system, when drawn as a map, should look like a tree with the battery's '-' terminal being the root. If any of those branches connect to other branches that's a loop and it will act as an antenna for RFI and EMI and can cause all kinds of grief with any electronics.

An EB has three main assemblies that need grounding. The engine/trans/t-c assembly, the body assembly, and the frame. Your highest current in any circuit is the starting current. For this reason I ground the battery to the engine block, preferably as close to the starter as is reasonably possible.
Can ground the engine to the frame, and the body to the frame, but don't ground the body to the engine as that completes a loop.
Can ground the battery to the body in parallel to the engine ground, and then ground the engine to the frame, BUT not to the body as that completes a loop.
Can ground the engine to the body and the engine to the frame, but do not ground the battery to either the body or the frame as that completes a loop.

Avoid more than one grounding cable between any two of the same assemblies, as that also creates a ground loop. If you can trace two different pathes to the ground terminal on the battery from any power consumer (lights, comms radio, stereo, electric fan, ECU, et., etc., etc.) you have a ground loop.

OEM's don't always follow this, but they know a heck of a lot more about what they're doing that I do. Safer to err on the side not making any loops.

 

[ntsqd]

That said, it sounds like you have a dedicated grounding system. Known as a "floating ground system" if no grounding circuit of a power consumer uses the body, frame, or power-train assembly for part of it's circuit. That's not a bad thing, pretty common on fiberglass boats and vehicles. Since the body and frame are conductors I would suggest that they be grounded to your grounding system, they just won't be carrying any current. Do this so that the body and frame are always at zero volts. This is exactly how I wired my avatar.

 

[AZ73]

Thanks. I'm going to have to review exactly what I did. I'm pretty sure I ran a wire from the neg battery down the passenger side, across, and up the driver's side and then grounded everything to it and the body or frame depending on the component, like side markers and headlights to the body and fuel pumps to the frame. I think I also ran a branch from this to a ground block on the back of the dash to ground all the gauges and dash lights to the block. I'll look back and see if I created a loop anywhere as you noted above.

 

[Steve83]

What you did isn't a "ground loop" (which is a very rare & undesirable effect in complex electronic circuits), and it's not even a "ground" (which is all the conductive structure of the vehicle). It's a "return wire system", which eliminates the need for grounding. Just remember that all the current that passes through all the fuses & wires going to all the electrical components must return through those new wires. So they'd better be large enough to handle it, or you could start a fire.

 

[ntsqd]

Bull-Puckey!
Any loop, any circular path in the grounding system is, by definition, a "Ground Loop." It is not a situation confined to electronic circuits. We should be so lucky. I have breadth and depth in this with a past employer, the hard way, and learned from it.

 

[Steve83]

Bull-Puckey!
Any loop, any circular path in the grounding system is, by definition, a "Ground Loop."

So every hole in the body (which is the "ground") is a ground loop? And every space between each pair of wire strands in each wire is a ground loop? Here's a bull for you to puck:

Ground loop (electricity) - Wikipedia

en.wikipedia.org

How about you post a link to the definition you're using?

 

[AZ73]

What you did isn't a "ground loop" (which is a very rare & undesirable effect in complex electronic circuits), and it's not even a "ground" (which is all the conductive structure of the vehicle). It's a "return wire system", which eliminates the need for grounding. Just remember that all the current that passes through all the fuses & wires going to all the electrical components must return through those new wires. So they'd better be large enough to handle it, or you could start a fire.

Yeah, I'm probably using the wrong term. I just figured I looped it around the Bronco (well, more like a "U". I used 12 gauge. So it should take 20 amps?

 

[73azbronco]

Bull-Puckey!
Any loop, any circular path in the grounding system is, by definition, a "Ground Loop." It is not a situation confined to electronic circuits. We should be so lucky. I have breadth and depth in this with a past employer, the hard way, and learned from it.

So I am going to have to disagree with this concept on the archaically simple EB setup.

Ground loops are bad in audio and higher functioning electronics. Also, anything new that uses pulse width modulation to code a unit in the system.

No you don't want the starter grounded from the block to the body back to the battery. Thats why I use fusible links, never had one blow. Thats why my 2000 Toyota did exactly what I did. So claiming a block to body small gage fusible link, then another wire grounding body to battery, then a huge gage battery cable block to battery is bad, is not based on the science. The least resistance path from starter to battery, is the large gage lower resistance block to battery wire. Does a little bit get through the fusible link, sure, not enough to worry about, and thats why they didnt worry about it in 1973. If what you say is true, my EB should have had multiple issues, it runs fine.

When I go to using an EFI setup, that will have only one ground to battery.

 

[ntsqd]

You can disagree all you want, but when a loop in a ground circuit causes a week plus delay in a $250,000+ DARPA funded development project and the Top guy on down are all looking at your group to figure it out you'll change your mind about what is and isn't a "ground loop". I am sticking with has been beat into me by painful experience as to what is and isn't a "Ground Loop."