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Best practices: Grounding?

Banjer Picker

Bronco Guru
Joined
Sep 25, 2006
Messages
1,357
What are the recommended spots to make sure our broncos are adequately grounded?

Wrapping up a new harness project and I keep hearing how crucial proper grounding is. Would be very grateful for recommendations.

I currently have:
-Painless fuse box grounded to dash
-Negative battery terminal to engine block
-Engine block (intake manifold) to firewall

What are other spots I need to connect besides the obvious grounds needed for accessories?

Would you recommend the flat ground straps?
If so is there a minimum specific size or gauge you would use?

Thanks!
 

El Kabong

Contributor
Driving stuff Henry built
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Oct 8, 2009
Messages
1,493
I always start with ground from battery to block, then from the same point on the block to frame. Both of those in 2 gauge or bigger, as well as #2 or bigger from positive to solenoid & solenoid to starter.

Then smaller grounds from frame and/or engine to body & other components.
 

DirtDonk

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...I currently have:
-Painless fuse box grounded to dash

Not sure I understand that one. Care to elaborate?
Just wondering how you grounded the fuse box, and why? Normally any fuse panel/box is just a pass-through with protection. No grounding because no flow wanted other than through the existing fused circuits.
Maybe I'm wrong about your particular fuse panel though, as there are some that have a convenient grounding stud for you to use as a handy central grounding point. But not any that I've seen on our Broncos.

-Negative battery terminal to engine block
-Engine block (intake manifold) to firewall

Perfect. Those are two very critical ones. As said, the one from the engine block to the battery negative should be as large a gauge as you're comfortable with (Ford used 6ga, but we often use 4ga, 2ga, or even larger nowadays) with the big one mounted as close to the starter motor as convenient, and to as clean and tight a location as possible.

What are other spots I need to connect besides the obvious grounds needed for accessories?

A direct line from the battery to the body is recommended. A 10ga wire is sufficient for most, but a little overkill is not out of line. Just that 8ga is so much more expensive and not easily available locally, so most of us use 10ga and it's fine.
I tend to run it from the battery to one of the attaching screws for the starter relay, but you can put it anywhere that's convenient to the body. Ford used the fender/wheel well area facing the engine and you can probably still see it on the inner face.

Another one is to the frame as mentioned. Most feel it's unnecessary, but anything that you want to ground to the frame later will thank you for it.

If you have an older rig (aren't they all?) with out much new sheet metal, you may find you need to run a wire from the inner fender to the grille/core support to help with headlights and turn signals.
Also the windshield frame is troublesome if there is rust. The wipers will thank you for a ground jumper to the main body (hidden behind things) if you do.
And finally the dash panel to the body. Keeps the gauges and radios and things happy.

If you want to get all up in it's face, grounding-wise, you could even ground the hood to the body near the hinge, and even the hard top to the body. Just to keep radio noise interference down more than anything else. Ford would ground hoods when an underhood lamp was used of course, but I'm pretty sure most manufacturers include the large metal hoods in their grounding scheme.

Most of that is overkill of course. But I'm into grounding overkill

Would you recommend the flat ground straps?

Sure. They work great, look cool in a "factory-ish" kind of way, and are already made up with clean ends.

If so is there a minimum specific size or gauge you would use?

Most of the standard ones for general use are the same two or three sizes. There are the small ones you find on the HELP rack in most stores that are probably more than heavy enough for most uses around the body.
Then there are the really heavy duty ones you find over on the same rack as the battery cables. I think they're a minimum of "4ga equivalent" or somewhere about there. That's what I've used between the engine block and the frame, but just like in all the other instances, what you use is up to you.
A 10ga wire with ring terminals soldered on are fine, as are braided straps. I don't really know, from an electrical theory standpoint, whether one is better than the other as a ground. Factories use both types too, so I figure they're roughly equal in function.

Paul
 
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OP
Banjer Picker

Banjer Picker

Bronco Guru
Joined
Sep 25, 2006
Messages
1,357
I always start with ground from battery to block, then from the same point on the block to frame. Both of those in 2 gauge or bigger, as well as #2 or bigger from positive to solenoid & solenoid to starter.

Then smaller grounds from frame and/or engine to body & other components.

Thank you for the input!
 
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Banjer Picker

Banjer Picker

Bronco Guru
Joined
Sep 25, 2006
Messages
1,357
Great and very thorough info Paul! I appreciate that level of detail!

Regarding my fuse block ground: Painless has a ground wire That comes from the fuse block in the glove box. Their recommendation was to ground it to the dash. My explanation may have been a little confusing.

Thanks again!
 

73azbronco

Contributor
Bronco Guru
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Nov 11, 2007
Messages
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I'm there now.

I'm running a 14ga wire, grounded with a nut/bolt, sanded to metal, then another bolt to attach grounds at:

drivers side core support behind headlight
Passenger side behind headlight
Then main ground on fender behind battery
ground strap from there to batt neg.

From that fender, inside to dash below instrument gauge grounding dash. Then from there out driver side down frame to rear frame, fuel pump.
Then one more to each side of the rear light bucket area.

Batt neg goes to block, alt bracket, frame.

I use short section of fusible link in ground circuit at fender and dash and rear end.

I am overkilling this. But I will never worry about a ground.
 

ransil

Bronco Guru
Joined
Sep 6, 2003
Messages
8,122
I run battery to block then weld a stud to the frame and inner fender close to this location and either use a strap or 8 gauge minimum to the frame and fender.
all light buckets get studs and ground wires run to the front common location,

I also use ground block ( glass and metal bodies)on the firewall and added grounds to all circuits and run to the common grounds.
I use these
http://www.vteworld.com/content/electromech/PDP/html/778Series/778Series.php
 

charlie6976

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Joined
Jan 19, 2014
Messages
404
Loc.
Grand Coulee WA
Engine to frame strap. Nick of Nick's Trix pointed out an unused bolt hole for easy grounding stap connection. The bolt hole is located in front of the right (passenger side) motor mount on the engine. Then drill and tap (I used a self tapping bolt). Then a standard one foot grounding strap fits nice. I think all small block Ford V8's. I have a Cleveland.
 

rguest3

Contributor
Bronco Guru
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Dec 13, 2012
Messages
3,778
Yep, I use that same location on the frame. Frame to Engine Block, Frame to battery.

I use a Blue Sea Safety Hub 150 for all my High Amp fuses and extra 1-30 Amp circuits. The Hub also has a Negative Buss included with a ground cable to the frame.
 

75MIKE

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Aug 22, 2001
Messages
955
Loc.
NE Washington
If you have an older rig (aren't they all?) with out much new sheet metal, you may find you need to run a wire from the inner fender to the grille/core support to help with headlights and turn signals.


Paul

What Paul said.

Mandatory when the aftermarket headlight harness with relays is used.

When your headlights blink when you hit a bump is a dead giveaway.
 

Steve83

Bronco Guru
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Jul 16, 2003
Messages
9,014
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Memphis, TN, USA, Earth, Milky Way
"Grounding" is commonly misunderstood...

When electricity first became publicly available (when Edison & Tesla were fighting over DC vs. AC), Copper wire was very expensive. So rather than run 2 wires everywhere, Tesla realized he could run a "hot" wire, and then use the ground (the actual dirt of the Earth) as the return circuit path. Inside a house, there still had to be 2 wires, but one of them went "to the ground" via a Copper rod driven into the dirt outside the house. That became known as "the ground wire". When vehicles acquired electric circuits (AFAIK, the first on any Ford was the electric horn, which Ford always numbers as circuit #1), it was equally-efficient to use the metal chassis of the vehicle as one the main electrical pathways, to reduce the amount of wire needed. And the term "ground" was carried over into that arena. Chassis grounding worked reasonably-well until alternators got up into the ~100A range (in the 80s) and vehicle wiring harnesses began to exceed the weight of the drivetrain (AFAIK, the first to cross that line was the '92 Lincoln Continental V6). Since then, more circuits are networked through high-speed data bus lines via communication modules so that you don't need a discrete wire running from one end of the vehicle to the other & another coming back to turn on a taillight, and confirm that the bulb isn't burnt out.

But as a result, the chassis/body ground is no longer sufficient to provide a reliable circuit path without introducing a lot of background noise (RFI) into those minuscule high-frequency data signals. So the trend for a couple of decades now has been to run actual Copper return wires so that far less current flows through the chassis steel. (House wiring standards added a return "neutral" wire decades before that.)

So by definition, if you're using a wire to return to the battery, you're not "grounding" that circuit - you're wiring it. And wiring it is a good idea when you're dealing with rusty 40- to 50-year-old body & frame steel. The catch is that the return wiring has to be AT LEAST as large as ALL the power wiring that it serves - IOW, very big like the alternator output wire, the starter wire, the winch wiring, and the ignition switch battery-supply wires. None of it needs to be bigger than the battery cables because you can't ever get more current flowing than the battery can put out (roughly whatever its CA rating is).

So if you want to be sure you have a good return path throughout any vehicle, just extend the battery (-) cable all the way to the trailer connector. Obviously, you can't run a cable that big into the trailer connector or anything else - you have to splice onto it to branch off with smaller black wire (or whatever color the particular circuit uses for "ground"). That's why I refer to that as a "trunk ground" system - the main return wire is like a big tree trunk, with the variously-sized smaller branches shooting out to hit each point on the vehicle that needs an exceptionally-reliable return (generally: the high-current devices; and those that require low RFI noise, like audio amplifiers).

Fortunately, those splices DON'T need to be insulated - they can be left showing bare metal. Both because they're all GROUNDED ;); and because Copper & solder don't corrode very quickly in air, or even in common rainwater. Mainly just at the battery where acid leaks out. Road salt will eventually cause some corrosion, but probably not enough to matter within the remaining lifespan of even the best-maintained early Bronco.

And the body & frame should still be GROUNDED at a few points, just to reduce galvanic corrosion, and to serve the very-low-current chassis-grounded loads like taillights & fuel level senders.
 
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ntsqd

heratic car camper
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Jan 30, 2005
Messages
3,274
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Upper SoKA
The flat woven ground straps are actually better at dealing with RFI/EMI than a typical wire. Ham guys, jump in here and talk about "bonding" a vehicle to reduce or eliminate RFI/EMI. When they do that the preference has been for the flat woven straps instead of wires. 80's-90's Toyota pick-ups are good JY donors for small, say roughly 10 ga. equivalent, bonding/grounding straps.

At risk of a certain someone jumping on my case I'll caution to run your grounds like branches of a tree and avoid any circular path in the grounding. Called a 'Ground Loop' and it can act like an antenna among other poor behavior. If there is only one path from any point in any circuit back to the battery on the ground side, you're good to go. If there is more than one possible you have a ground loop and it may or may not give trouble. Best to just avoid it.
 

ntsqd

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Like I said....

If you create a ground loop and your EFI starts acting up perhaps you created that problem.
 
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Broncobowsher

Total hack
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34,980
#2 ground cable to the frame is a waste of good wire. Please list the electrical load on the frame that requires such a massive ground. The engine and body all sit on rubber mounts.

An exception to that would be a winch that is grounded to the frame. But in that case I would run a ground from the engine block to the winch. Why the engine and not the battery? The alternator is grounded to the engine. Hopefully you have the engine running. Less loss going from the alternator to the winch instead of to the battery than to the winch. Let the battery supplement the winch power instead of the alternator supplementing the battery power.

It was common to see a braided ground from the cowl to the hood on a lot of cars. That was to help suppress RFI. Old Corvettes had sheetmetal shrouding around the spark plug wires since they didn't have a metal body to suppress RFI noise.

I was once bitten by a bad ground on an EFI install. There was only 1 ground between the battery and the body, none between the engine and the body. Just a battery to engine. That is the body and engine had a ground through the negative battery post. The EFI was grounded to the body. The O2 sensor was grounded to the exhaust (engine). It would run full rich only at night. One night while fighting it I was watching the EFI parameters. The O2 looked OK but it was rich. Shut the engine off. Turned off the headlights and the O2 voltage changed. Turned the lights on, off, on, off. The O2 voltage would swing with the headlights. The engine lacked a direct ground to the body.

I changed to the logic. The center of the electrical world is the engine. It has the starter and alternator attached. Everything else is supplemented off that. The body is attached to the engine. The battery is attached to the engine. The winch is attached tot he engine. The engine is the ground reference. Once I took that approach I have not had rounding issues with any project vehicles. And fixed a good handful of other peoples issues by using that same approach. Often it is nothing more than just moving the sequence of how the grounds are connected. Gets rid of the rat's nest of wires on the battery post. Cleans so much stuff up.
 

ntsqd

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Using the engine as the reference ground I think is a great idea, but one note of caution. I once had a truck with two starting batteries that would kill each other. They were both grounded to the block, but in different places. There was enough resistance between them that it set-up the see-saw discharging cycle.

So, with high current grounding to the block I strongly suggest when possible using the SAME bolt. The low current demands I don't think are as important, but if an EFI system is behaving badly I'd look into it.
 

Steve83

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#2 ground cable to the frame is a waste of good wire.
I agree. Even on newer EFIs with factory 130A alternators, the battery cables are 4ga, so nothing on a stock eB needs to be larger (lower #) than that. A winch should have its own wiring (sized for the winch) directly to the battery terminals.
Less loss going from the alternator to the winch instead of to the battery than to the winch.
Loss (resistance/voltage-drop) is directly proportional to load (current/Amperes). The battery is ALWAYS capable of supplying more current than the alternator, so that's where the heaviest loads belong (like a winch). If you make a lot of current flow from the battery through either battery cable to a terminal to the block to another terminal through another wire to the load and back through another one or two cables to the battery, you will inevitably have higher resistance than if it only has to go through only 2 cables total. Especially if they're soldered into the battery terminals.
The center of the electrical world is the engine.
The "center" of any electrical system is the voltage source (battery all the time; plus the alternator only when the engine is spinning). If any part of the vehicle's wiring is "off-center" (a voltage difference from the source), it indicates a fault (resistance) in the wiring that needs to be repaired - not worked or wired around. Particularly if the engine block is ever at even a SLIGHTLY-different voltage than the battery (-) post or the alternator case; regardless of load.
 
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73azbronco

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On the ground loop concept in an EB, I think the body to frame issues are a loop in and of itself. Your headlights say ground to the front body, returning through the body to closest body mount, to frame, to engine mount, to block to battery.

That's noisy right there.

My running one wire direct from locations back to battery gets rid of any looping effect. I do not have a loop of ground going around the car.

Good news, for 90% using old school carb, ground loop is no issue.

For the 10% needing a computer to process digital/analog info, ensuring your power and return go directly off the battery posts eliminates the noise issue. In fact both Mallory ignition and Holley sniper both demand their power come directly from the battery, and directly ground to the battery.
 
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