Alternator wiring

[Thatbroncokid]

Recently found out my alternator wasn't charging my battery. Noticed this big yellow wire coming from alternator harness and can't figure out what it does and if this might be my problem. I've looked at diagrams for alternator wiring but I can't really understand them. I'll attach pictures of the wire and voltage regulator. Thanks!

https://ibb.co/fBLe47
https://ibb.co/cO73Wn
https://ibb.co/fp2gHS

 

[Rustytruck]

In your second picture unbolt the voltage regulator and clean the rust and crud off the regulator and the firewall and the mounting bolts. The regulator needs a good clean ground to the body. The body needs a good clean ground to the negative side of the battery.

 

[Thatbroncokid]

In your second picture unbolt the voltage regulator and clean the rust and crud off the regulator and the firewall and the mounting bolts. The regulator needs a good clean ground to the body. The body needs a good clean ground to the negative side of the battery.

Okay great I'll try that. My negative post is grounded to my block if that makes any difference.

 

[DirtDonk]

That, but it also looks as if that wire you're holding is a ground wire that a PO might have added to make things work better.
Before you remove the regulator, either disconnect the battery or unplug the connector at the regulator so it's not connected.
Not sure if it will always bugger a regulator or not, but you "can" fry a regulator by running 12v to it with no ground. Not sure how that works, but it's been mentioned here many times by those who know a lot more than me about that stuff.

While it's disconnected, check voltage on the 3-wire connector to make sure the circuits are functioning.
The positions might be marked F, S, A & I. On an EB, only the first three are used. On cars and trucks with lights instead of an ammeter, all four are used in a different order.

On yours, you should have:
1. An Orange wire at F (field).
2. A Green w/red wire at S (stator, or in our case "switched")
3. A Yellow wire (or two) at A (armature, or in our case "always hot")

The Yellow wire (in the regulator plug) should be battery voltage all the time. Check it to make sure it's within a fraction of a volt of actual battery voltage.
The Green w/red wire should have battery voltage when the key is in RUN (but not ACC)
The Orange wire should just have good continuity between the connector and the back of the alternator on it's FLD terminal.
The I position (ignition, or "indicator") is blank

You have a second Yellow wire there that I can see that does not go anywhere. Originally there would have been a capacitor thingy for radio noise reduction. Same thing on the positive side of the ignition coil at the Red w/green wire.

So it's easy to at least test the wires and connector. Not so much the regulator itself.
If you jump a wire straight from the battery to the Orange Field wire (or just from the yellow A wire to the Orange F wire in the connector) you can fire up the engine and see if the alternator is charging the battery. This can be seen by either watching the ammeter go up or by measuring voltage at the battery. Should be 14.5v when the alternator is working normally, but can be as high as 16 or 17 while you have the jumper wire there. So it's not a good idea to run the engine longer than it takes to test the voltages. Batteries don't like overcharging, but can take it for a few minutes without trouble.
If you're not sure about all that, it's also easy to take the alternator in to an auto parts store to have tested.

If all that stuff checks out, likely you just need a new regulator.

Good luck

Paul

 

[DirtDonk]

The main cable of the battery's negative is supposed to go straight to the engine block. Closer to the starter motor the better in fact, because the starter is the main reason for the cable and is the largest user of current on the truck.

Also on the negative side of the battery you should have a wire running down to the body. A good place is to one of the bolts holding the starter relay in place, but you can put it just about anywhere.
If your negative battery cable is original, it's already grounded to the body through the clamp into the wheel well. But if it's that old anyway, it's not a bad idea to replace it.
Always get a negative battery cable with an extra wire, so you can make your own ground to the body like Ford did originally.

You'll hear it said here a lot, that there is no such thing as too many grounds. And with Broncos it's pretty much gospel! They were just barely sufficient from the factory, but add 40-50 years of rust and paint and flex and dirt, and the connections (bonds, in the parlance of grounds) have deteriorated to the point that they don't always conduct the cleanest electrical currents through their contact points anymore.

What year is your Bronco? Looks like a '66-'68, or even 69 maybe?

Good luck.

Paul

 

[gooch66]

I had the same problem last week and it was two wires connected to the voltage regulator. Once I made sure the connections were good, battery is charging again.

 

[Thatbroncokid]

Thanks for all the replies! I'll definitely try all of that stuff. The truck is a 1970 actually! Love this forum. Lots of stuff to try tomorrow.

 

[Thatbroncokid]

So I did everything, and didn't get any results except for when I jumped the field wire to the yellow wire. At idle I was getting 13.3 ish volts and it would go up around 16v if I revved it. Took the voltage regulator out of my other bronco (also a work in progress), and still didn't have any luck. So the alternator is "good", and I probably have two fried voltage regulators?

 

[DirtDonk]

That's always a possibility. Not many other things it can be at this point. Other than perhaps an intermittently loose wire connection maybe?

Or your alternator is weak possibly. That 13.3v does mean that it's charging. It's just not charging a lot. Which is not out of line for an older 1G alternator.
That 13v should at least keep the battery charged when very little drain is placed on it.

So what was it that led you to say the battery was not being charged in the first place? Was it going dead every time you drove it? Short trips, or just starting multiple times and shutting it off for testing? Maybe the battery getting lower and lower over time?
Or something else?

Next time you're out there with your voltmeter, turn on the engine, let it idle and check for voltage again. If you get that same 13.3-ish at idle (what's your idle speed by the way?) then rev up the engine while watching the volt reading. If it goes up with rpm, then the alternator is simply weak at idle.
Which most of them were, but they could at least keep the battery charged even at idle when in good shape.

So it could still be the alternator.

Paul

 

[DirtDonk]

I forgot to ask. Is this Bronco new to you, or have you had it awhile? If new to you, do you know if the battery was ever being fully charged?

Paul

 

[Thatbroncokid]

I should confirm, it's only getting 13.3v when the wires are jumped together. It doesn't get any charge at all when the wires are hooked up as they're supposed to be. I test it a lot in my driveway as it's just about road ready, and it would eventually need a charge every couple weeks of starting and stopping the engine. Just now decided to look into it. I've had it a while, but never on the road so I can't say for sure.

 

[DirtDonk]

Ok, sorry I misread your previous post.
Then I'd have to say that yes, your alternator is "good" or at least good enough for now, and you should try another voltage regulator.

As we mention here all the time, it's way too common to get a bad part right out of the box. Poor manufacturing quality, and poor habits in the stores that very likely result in a defective return part going right back on the shelf when someone doesn't know what to do with it.

Even the warehouses join in the fun sometimes. In the past when I was doing some warranty work, or re-arranging shelves, or re-boxing parts with the new "manufacturer du jur" I'd find obviously defective mechanical parts on the shelf waiting to go to their customers.
Luckily with most of that stuff it was visually obvious. Unlike an electric part that you don't know until you try it.
Either way though, getting a bad part, or an obviously borked warranty return while you're under the gun to fix your ride is frustrating no matter what.

Long story longer, just to say, don't trust all the new stuff. If all your tests indicate the alternator should charge, and all your wiring/voltage tests indicate that the two regulator wires in question get consistent readings, then it's a good bet your regulators are bad.

There used to be ways to test regulators too, back when they were operated by mechanical points (just like a distributor) but I think those tests may have gone away with the advent of electronic units.
Unless someone knows of a good test for regulators?

Paul

 

[Thatbroncokid]

Okay everything you say makes perfect sense. Any suggestions on voltage regulators to pick up?

 

[DirtDonk]

Not sure. They're probably all a crapshoot these days. Overseas electronic stuff as replacement auto parts are not proving to be very good. At least when compared to the cell phones, TV's, and other electronic entertainment stuff that comes from the same countries and that seem to work very well.
Apparently we don't set the standards for their auto parts manufacture very high.

But that said, maybe a Motorcraft brand regulator? Echelin? Standard Motor Products still good? Not sure, since they're all likely imported, but so far we've seen Motorcraft branded stuff keep a reasonable reputation.
For now...

Good luck.
Lots of them purchased by members here, so someone will likely have some good recommendations. The stuff I bought is mostly very old now and still working fine.

Paul

 

[Thatbroncokid]

You're the man, thanks so much!

 

[Thatbroncokid]

New voltage regulator fixed the problem! Thanks so much for the help. Don't know what I'd do without this forum! (especially Paul lol)

 

[DirtDonk]

Hey, a result!
They do go bad over time. Guess it was just time for yours.

Paul