Where are teh electrical ground locations from factory?

[clintonvillian]

I assume there was:

Ground to body
Ground to frame
ground to motor

motor to frame?

This thing is all jacked up...

That engine ground is going to a water pump bolt.....

 

[DirtDonk]

Not the best place.
A "best practice" is to run the main battery ground cable to as close to the starter motor as possible. Even if that means all the way to a starter bolt.
In lieu of that however, any available bolt (but not a head bolt!) is legit and Ford put them on the block just below the head and behind the alternator. I've found a threaded hole on the side of many 302's just about mid-way back to the starter that is the perfect spot for some I've done.

Yeah, looks like kind of a mess.
In the original Bronco world, there was just the one negative battery cable (probably 6 gauge) from the battery to the engine block, but with a stop at the wheel well just there around the corner from your starter relay (aka solenoid). If you reach around you will probably feel a small screw hole where it was originally grounded.
When the battery cables are replaced, probably 80% of the people never get around to putting on a body ground.

There was no frame ground on our Broncos, and for some unknown reason Ford did not even think it was necessary to put the usual ground strap between the back of the intake and the firewall. Like they did for most every other vehicle starting sometime in the late sixties I think.
I guess they figured that having the fenders welded to the tube, that was good enough. And it was when they were brand new! But add 50 years of paint, rust, and general separation anxiety, and one of the best things you can do to your Bronco is to add grounds to some of those places.

My recommendation these days if you're using store-bought battery cables is to get 2ga (because it's overkill, and overkill is a good thing with battery cables) and make sure the negative side has the extra 10ga "pigtail" sticking out that you can crimp some extra wire to and run down to the fender or wheel well.
Then add a ground jumper between the engine and firewall and the engine and frame.
You can use plain old 10ga wire, or you can get some of those pre-made braided straps with ring terminals already on each end. They work great and are usually found on the HELP! rack at any parts store.

Then "while you're at it" again, add some additional grounds inside the cabin.
One from the firewall to the metal dash, and if needed from the dash to the instrument cluster.
Yes, the cluster "should" get a very good ground from the four screws that attach it to the dash, but here again that ain't always so.

Just FYI with Bronco grounds, several of us have even run into Broncos that had to have extra jumper wires attached between the radiator core support (where your headlights and turn signals get their ground path) and the inner fenders where the battery ground is. The old spot welds are just not enough to get good flow sometimes.
The other oddball area is the windshield frame. Yes, it's theoretically got a fantastic connection to body sheet metal, but rust seems to reduce that effectiveness.
I have not run into it often, but if you ever have wonky wipers, sometimes it's just the frame in need of a good new ground.

Fun, huh?%)

Paul

 

[DirtDonk]

Oh, and another FYI. NEVER EVER EVER throw away your old starter relay! Not until you have fully determined it's bad anyway.
Or any other part for that matter, until you're sure it's dead.

The problem is the quality of the new stuff is absolutely in the dumpster. There are loads of discussions about brand new ones only working for a few starts, or a week or so. Or not working right out of the box.
It's so bad that I bet at least 40% of them are not lasting very long, or at all.

The suggestions for possible cures are to only buy the big dollar ones with big names like Motorcraft, or better yet go to the junkyard and find an old original for a couple of bucks!
In most cases the old original Ford parts will continue to outlast the new cheapies form overseas.
Not sure what you get if you go to the dealer, but if they show you the box and it's made anywhere with a good reputation, it's probably better than your typical aftermarket stuff from the discount auto stores.

However, if you find one of these, you can get the warm-n-fuzzies for the good old days:

That right there is a starter relay from Borg Warner that was made in the USA! Not sure if it's possible to find those anymore. I probably bought it 35 years ago.

I paid more than $60 bucks for a marine certified Volvo/Penta Ford starter relay. I have not used it yet, but I figure it's probably as good as you can get these days.

Paul

 

[DirtDonk]

Sorry to keep pelting you with stuff, but another thing you might run into is the incorrect wiring at the voltage regulator.
Ford used two distinct wiring schemes for their alternators, with one used in most vehicles, and the other used strictly in vehicles (mostly trucks) with ammeter gauges rather than just the charge indicator light.

Since Broncos had a great ammeter, they also got the oddball wiring.
So just be careful when you're looking at wiring diagrams, or you're familiar with other Fords, and the wiring at the regulator looks funny.

When you get to that point, let us know and it's easy to run them down wire by wire to make sure it's all working.

Paul

 

[73azbronco]

Only grounds I know of stock are a wire to left rear lower body by fuel filler hose for lights, the battery ground to engine block. I think there is a dash ground wire to instrument lights to dash, and a ground wire for overhead light to windshield. Headlight and horn ground to front =body as well. OK thats all?

 

[papy]

good info- following.

 

[B RON CO]

Hi, the fuel sender is grounded to the rear cross member. I added negative terminal to core support and engine block to body and chassis using existing bolts. Good luck

 

[Steve83]

AFAIK, the original "grounding" scheme was:
B- to starter mounting bolt or front block tab.

(phone app link)


Alternator case post to V.R. mounting screw, which grounds fender/starter relay/body/etc.

Intake manifold to firewall, which grounds dash/body/etc.

I've never found how the frame was originally grounded (maybe through the steering shaft), which probably explains why the rear fuel gauge is so flaky.

But to build a good ground system on an eB, just mimic a later one, as described in these captions:

(phone app link)


(phone app link)

 

[Steve83]

If you REALLY want it to work well, don't rely on grounding. Add true Copper return wiring throughout the truck so the grounding is only for RFI.

(phone app link)

 

[DirtDonk]

To my knowledge Steve, Ford never installed an intake-to-firewall ground strap on Early Broncos. To this day I've never seen one that was factory installed, even on original '77's that I've known.

And the battery-to-engine ground cable was the body ground as well, accomplished with the small "mounting clamp" that was screwed to the inner face of the wheel well (facing the exhaust manifold). This tab was metal and in full contact with the wire conductors where the outer protective jacket was left off and the strands were exposed.
The strands looked tinned (if that's the proper description in this case?) and did not rust very quickly. Took a LONG time for them to rust, and generally the whole cable was needing replacement before the exposed strands showed their age.

I don't think there was ever a separate frame ground on Broncos. Obviously it was used for fuel senders as their ground path, so you might be right about the steering box/shaft, or if there is any conductive path of metal in the engine mounts(?) that could be it.
I know they're fully rubber isolated, but I wonder if there is any metal-to-metal contact inside of them?
Never seen a separate strap or wire between the frame and any other component in all my crawling around. Hence my usual recommendation for adding one, along with an engine-to-body ground whenever doing any re-wiring projects.

Paul

 

[DirtDonk]

Perhaps there was some conductivity through the speedometer and parking brake cables too?

Paul

 

[DirtDonk]

Here is what's left of a stock original after it was apparently cut, or failed due to over-working perhaps.
Note the metal clamp. If you look on any Bronco you will find the stamped hole for that mounting screw in exactly the same spot on all year models, except perhaps for '66. But I think they had them in '66 too.



This feature is also why most EB's that have had at least one negative cable replacement no longer have a body ground. Most people don't even think about that tab being a ground contact point and simply install a new standard cable.
The correct type of cable to get through the aftermarket is one with the additional "pigtail" for use as a body ground.

Paul

 

[Rustytruck]

My 1974 bronco was negative wire from battery post to blockblock below #2 plug down low at the pan rail. On its way down ther was a metal flag on the wire that was bolted on the front of the passengers side inner fender. There was a wire from the inner fender behind the fresh air plastic duct to the negative battery terminal. There was a ground wire from the bolt holding the auto dipstick tube to the firewall important grounding issues are tail light harness to the frame to the frame back by the drivers side rear bumper opening. The horn grounds through the steering collumn and used a special conductive steering rubber coupler. The voltage regulator mounting bolts are an important ground point as are the mounting bolts for the starter relay. The horn relay on later models grounds through its mounting bolt as do the horn mounting bolts. The gauge cluster has a ground connection. The turn signal and tail light buckets ground through their mounting too.

 

[charlie6976]

Engine to frame ground. Nick's Trix , of Nick's Trix, once pointed out that there is an unused threaded bolt hole on small block Ford engines that can be used for a ground strap connection. This threaded bolt hole is located in an ear at the front right side of the engine below the number one spark plug. Just need to drill a hole in the frame. Run a tapping bolt in the fame hole for threads, then I switch out to a regular bolt. Then a one foot grounding strap.
By the way, I have a fiberglass body, so return grounding wires are sometimes a must.
Hope this helps.
Thanks to Nick at Nick's Trix.

 

[DirtDonk]

I've used self-tappers for the frame, but I've also found the bolts holding the motor mounts to the frame work well too.
And in one case, if I remember correctly, even though the mount towers were welded to the frame, one of my trucks also has them bolted. Pulling one of the bolts, cleaning the surface and running the ground strap to that worked out great.

As you're seeing from the answers, you don't really care what Ford did on the Broncos originally, since our EB's were woefully under-served in the grounding department. So adding your own and bringing it up to more modern standards is a "best practice" when it comes to Broncos.
Just mimic any car from the early '70's vintages on up, then add a few of your own by need and you'll be in great shape.

Paul

 

[Steve83]

...Ford never installed an intake-to-firewall ground strap on Early Broncos.

I guess that came with the replacement engine that was in Frank's '75.

...any conductive path of metal in the engine mounts(?)...

Not intentionally or reliably.

Perhaps there was some conductivity through the...parking brake cables too?

They aren't actually attached to the frame; body to axle only, and the axle is insulated by the leaf spring bushings.

Here is what's left of a stock original after it was apparently cut...

View attachment 504785

I can't tell from that pic - is the insulation removed inside the clip, like this shows?

(phone app link)

...there is an unused threaded bolt hole on small block Ford engines...in an ear at the front right side of the engine below the number one spark plug.

That's what my first pic above shows.

...add a few of your own by need and you'll be in great shape.

That's actually riskier than it sounds. Having multiple ground paths can create serious problems under a few very-specific & -rare failure modes. For example: if you have a small return wire from the alternator to the battery, in addition to the main for the starter/block; and you change the starter but forget to re-attach the big cable before you hit the starter, all that current flowing through the small "extra" wire can set it on fire. So it's best to have a single wire path from any one device to & from the battery. Just like splicing an amplifier's big power cable to the original radio circuit; if the amp's big fuse blows, it'll then burn the small original fuse. But on the negative side of the circuit, you're burning wires that aren't supposed to be fusible links. You can have many devices share a wire (if it's large enough for all their loads), but don't have several wires share one device. Look at this later factory return-wire scheme, and you'll see how things come together to get back to the battery negative - they don't split to get there.

(phone app link)

 

[DirtDonk]

I can't tell from that pic - is the insulation removed inside the clip, like this shows?

(phone app link)

Yes. It was generally very cleanly done, with little of the conductors visible on either side of the clamp and no real bunching up of the outer covering.
It might explain why so many people miss it in fact. To the casual observer it may just seem like a locating clamp, and not an actual conductor.

Paul

 

[charlie6976]

I guess that came with the replacement engine that was in Frank's '75.Not intentionally or reliably.They aren't actually attached to the frame; body to axle only, and the axle is insulated by the leaf spring bushings.I can't tell from that pic - is the insulation removed inside the clip, like this shows?

(phone app link)
That's what my first pic above shows.That's actually riskier than it sounds. Having multiple ground paths can create serious problems under a few very-specific & -rare failure modes. For example: if you have a small return wire from the alternator to the battery, in addition to the main for the starter/block; and you change the starter but forget to re-attach the big cable before you hit the starter, all that current flowing through the small "extra" wire can set it on fire. So it's best to have a single wire path from any one device to & from the battery. Just like splicing an amplifier's big power cable to the original radio circuit; if the amp's big fuse blows, it'll then burn the small original fuse. But on the negative side of the circuit, you're burning wires that aren't supposed to be fusible links. You can have many devices share a wire (if it's large enough for all their loads), but don't have several wires share one device. Look at this later factory return-wire scheme, and you'll see how things come together to get back to the battery negative - they don't split to get there.

(phone app link)

Steve, why did you dissect my post? You took out the part about how to install the grounding strap. By using less than one sentence from my post, you made it look like your post except without a picture. I don't understand your point?

(I am not good on computing skills, however.) wrong quote

 

[DirtDonk]

My take on it Charlie is that Steve was simply reinforcing yours (and his too) statements. At least I did not take it as any kind of correction, but more of a "here is a picture of what charlie6976 was talking about" kind of thing.

Of course, I could be wrong, but that's how I took it anyway.

Paul

 

[charlie6976]

I just thought it strange he left out the strap installation part. All is fine.