Stock Alternator Wiring and Overall Engine Wiring

[zsmith]

Ok so I am struggling with doing the engine wiring on my bronco, specifically making sure my grounds are where they should be and my stock alternator wiring. I know this should be basic stuff but need some wiring 101 I guess. I have the manual but it isn't specific on how to wire up the alternator and where my grounds should go. Any help with this would be really appreciated.

Thanks!

[DirtDonk]

Re: Stock Alternator Wiring and Overall Engine Wiring

I see your problem... That's no alternator, it's a dead fish!
Oh wait, that's just your avatar... Oops.

So whatcha got? All stock with external regulator? This for the '70 in your sig?
First, whenever looking at wiring diagrams, make sure to ignore any that are used with an indicator light. They're wired completely different than one of ours with an ammeter in the dash instead.

With that in mind, and an all-stock harness, which alternator connector assembly do you have? Got a pic, since there were three or four used over the years.
Basically though, going by wire color only, your connections will go like this:

1. Large Black w/yellow stripe (stripe may be hard to see or completely MIA, but you'll know what wire it is by it's size and connector) goes to the large terminal on the back of the alt with the red insulator and may even be marked "BAT" or "CHG"

2. Very small Black w/red stripe connects to any one of the small GRD studs coming straight out of the alternator's outer case. This is the ground, but with a stock harness connector, it's likely to be just a little ring sticking out the side of the main rubber insulator/strain relief.

3. Orange is the "Field" wire and connects to the mid-sized stud with the Orange insulator base on the back of the alternator. This and the previous ground wire are the only two that go to the regulator

Verify the order of the voltage regulator's four terminals. They should be marked "F, S, A, I" somewhere. Usually on the connector lock tab.

4. Orange wire to the "F" terminal on the regulator.

5. Green w/red stripe wire from the ignition switch (hot in RUN only) to the "S" terminal on the regulator.

6. Yellow wire to the "A" terminal. It is hot all the time and should have full battery voltage. From the factory it's most often spliced right into the main harness near the battery and starter relay, and is usually a reliable connection, so unless you've had it all torn apart, it's probably still good. Sometimes, if they've been messed with or melted, or you just have to make a new one for some reason, people will most often simply connect the Yellow wire to the battery side of the starter relay.
Later EB's starting in about '74, started using a horn relay mounted to the fender wall near here, and had a Yellow power wire run to the battery terminal on the starter relay. If you're using a later model harness, don't let this Yellow wire with large ring terminal confuse the issue with a voltage regulator.

6a. A second Yellow wire with bullet-type connector is spliced to the first Yellow wire and has a radio noise suppression capacitor at the other end. It's usually attached to the fender using one of the regulator's mounting screws.

7. The small Black w/red ground wire from the alternator will also utilize one of the regulator's mounting screws.

For grounds, make sure that your alternator's mounting pads on the engine block/head are clean and unpainted. This allows the alternator to ground through it's body to the engine. When upgrading to high-output alternators, I actually add a ground cable from one of the mounting bolts to wherever.

Good grounding practice:

1. Make absolutely sure that your battery's negative cable lug has a secondary wire of at least 10ga running to the body (usually the fender)

2. Try to mount the main cable (4ga or larger is best) to the engine block as close to the starter motor as possible. Not absolutely necessary, but good practice.

3. Add a small-ish ground wire/cable between the engine and the body. Usually a braided cable between the intake manifold and the firewall is the factory practice. For some reason they never did this to EB's, even while they were doing it to literally every other car and truck they made! I like the braided wires myself, but a nice 10 gauge wire will do the trick nicely. Or, if you're a junkyard maven, there are some really sanitary ones that are braided, but with a rubberized coating on them and soldered on rings at each end. I think I've seen these on Explorers and similar rigs.

4. Another good practice that I've been seeing others do, and so doing myself, is adding another ground jumper between the engine block and frame. Again, it's not really needed, but it's a nice addition no matter how you look at it. And it's so convenient and inexpensive, why not, right?
904Bronco here typically uses a short section of 6ga or 4ga cable (or whatever is being used at the battery) to run the jumper between one of the front cover bolts and the frame crossmember.
We put a nice store-bought mondo-large-o braided battery cable on two rigs recently. One was SteveP's just finished (almost?) '73 and another on TomR's uber-cool '46 Willy's Jeep.
Like I said... Why not, right?

Have fun!

Paul

[welndmn]

Re: Stock Alternator Wiring and Overall Engine Wiring

Ditto what Paul said.
Or, just dump that stock 45-50 amp alt and buy 1 wire 130amp 3G alt from wild horses.

[ntsqd]

Re: Stock Alternator Wiring and Overall Engine Wiring

Not a fan of one-wire alt's myself. If you do have a battery kill switch (DD has one, EB about to get one), which I doubt the OP does, but if you do they make the wiring more - not less - complicated. They also have a fairly high stator speed threshold before they start to charge. That may have changed, been a while since I've looked into them in depth. I want an alt that I can buy off the shelf from the NAPA in Carver's Jct., NV or John Day, OR, or similar so I haven't bothered keeping up with them.

[zsmith]

Re: Stock Alternator Wiring and Overall Engine Wiring

Thanks guys. I am going to work in it tomorrow! I'll send pics if I get stuck��. Thanks paul for that detailed post it is exactly what I need!

[zsmith]

Re: Stock Alternator Wiring and Overall Engine Wiring

Here is a pic of the back I don't have a connection for A stud. How do I fix that?

[Viperwolf1]

Re: Stock Alternator Wiring and Overall Engine Wiring

Paul was referring to the voltage regulator connections above. You have every terminal you need on the alternator, BAT (battery), FLD (field), STA (stator), GRD (ground).

[zsmith]

Re: Stock Alternator Wiring and Overall Engine Wiring

I don't have a connection for the A post on the alternator in my current alternator wiring pigtail (it is the black post that my finger is on in the picture). Do I need that and if so how should I wire it? Thanks a ton guys!
Z

[Viperwolf1]

Re: Stock Alternator Wiring and Overall Engine Wiring

I don't have a connection for the A post on the alternator in my current alternator wiring pigtail (it is the black post that my finger is on in the picture). Do I need that and if so how should I wire it? Thanks a ton guys!
Z

The alternator pigtail doesn't have it because that wire is part of the main harness coming from the starter solenoid. You probably never had a wire on the STA terminal of the alternator because it was used only with the stock electric choke.

[904Bronco]

Re: Stock Alternator Wiring and Overall Engine Wiring

The alternator pigtail doesn't have it because that wire is part of the main harness coming from the starter solenoid. You probably never had a wire on the STA terminal of the alternator because it was used only with the stock electric choke.

Choke only had power from the STA when the rig was running... No power when off.

[zsmith]

Re: Stock Alternator Wiring and Overall Engine Wiring

Thanks guys,

Yep it is a manual choke on mine, but that is good to know for future reference!

Zach