Low Voltage Issue

[DirtDonk]

Very possible. We run into "coincidental failures" LITERALLY ALL THE TIME!
Of course, one could have led to the other I would presume. I don't know what causes a FLD terminal to go wonky inside an alternator, but anything seems possible with these things sometimes.

Was there still a plastic insulator between the stud and the body of the alternator?

Paul

 

[BanditBronco]

It sounds like you are getting close to figuring out your issue, I did want to input that the charge wire in the centech harness is rather small gauge considering and it is run through the fuse panel before heading to the battery. I had a 1 volt drop between my alternator and the battery on the charge wire. Might check that too. I know its controversial but I ran a larger gauge direct to the battery from the alternator to try and help with my low voltmeter readings. It helped but I also don't ready a bunch over 12V when charging. I definitely don't see 14V which would seem to be the standard for an optimized charging system. Also for reference this is with an explorer style alternator on a centech body harnessed rig.

 

[DirtDonk]

I had a 1 volt drop between my alternator and the battery on the charge wire.

Was that on the Centech harness? That's a lot more than I would have expected from the new wires. Even as long as they are, I thought a clean 10ga wire would not have that much drop.
Don't remember checking before, but I will next time.

I know its controversial but I ran a larger gauge direct to the battery from the alternator to try and help with my low voltmeter readings.

Also for reference this is with an explorer style alternator on a centech body harnessed rig.

Nothing controversial at all. Or should not be. It's what all the factories do, and the only thing that it changes on an Early Bronco is you lose the ammeter's full function.
BUT! And this is a big but... That's what you're absolutely supposed to do with anything even approaching an Explorer alternator's 130+ amp output capability!

The stock wire, and even the new replacement Centech wire, were never expected to pass more than 60a or so. Certainly not the typical 95 or 130 amps from a modern alternator for any amount of time.
Yes, Centech claims that it can handle 100a, but I'd say that's probably close to being maxed out and probably not a good idea to test that theory for the long term

So you did the right thing no matter what. It's exactly how Ford wired your Explorer alternator, so is how anyone who's swapping one in should as well.

It helped but I also don't read a bunch over 12V when charging. I definitely don't see 14V which would seem to be the standard for an optimized charging system.

That's extremely strange for any setup like you have. That 14v is definitely the expected voltage. It's what I've seen on every setup, whether Ford, GM or just about any other I've worked with.
I'll check mine again the next time I think about it, but every other vehicle I've ever owned has read consistently in that 13.5-15 volt range at various times. With 14.5v being the most common reading.
The new computer controlled rigs (sometimes the voltage regulator is the ECU in fact) will vary the output based on need vs conditions. Lowering the load when the battery starts getting hot.

Does yours give you any trouble? Working fine in the long term so far? You're taking the readings right at the battery terminals? Checked your meter on another vehicle just to be sure?
Very curious how yours pans out over time. Even the OP's does not seem to be dying quickly, even though that one only shows 12v all the time. Either there is something else at work here, or that's one heck of a battery!
I want one...;D

Paul

 

[EastcoastMike]

I got it charging at 13.4 at idle tonight. I ran a new wire to the alt. Field lug and jumped it to the positive battery terminal. Bingo.

I tested the disconnected field wire and it was dead now. Upon closer look, the insulation on the connector was pretty janky- maybe it was grounding to the alternator case at that point. I’ll throw an new connector on when I get a few more mins to mess with it and work my way back to the regulator and figure out the green wire issue next.

Thanks again for all of your wisdom and patience.

 

[DirtDonk]

The Green wire should be easy. It's got one path, straight to the from the ignition switch to the regulator plug.
It shares a lug on the back of the switch with the ignition coil's Red w/green wire, so you know that the switch is and contact is good because the engine runs. So the fault must lie somewhere between that connection/splice at the back of the ignition switch, out through the firewall and to the regulator.
It's not a very common failure point though. Rarely have I seen one that was not working under the dash unless a PO added a tap or scraped the insulation off while working around it.
Under the hood however is a pretty harsh environment so I'd start at the regulator connector and work your way back to the firewall. Maybe at the connector itself? Rust, broken insulation?

Check it out and see if you notice anything that does not look right.
Just like the janky insulation on the Orange wire in fact. Maybe someone was messing with them all and was not too gentle about it.

Paul

 

[EastcoastMike]

Mystery solved. A little embarrassing, but I’m new to this. I peeled back the loom and began following back the green wire to the firewall. At one point the wire goes into a plug with some dead ends that were covered up. The green wire label changes from “Reg” to something else at that point, and then continues to the fuse block. Here’s what happened:

1. I didn’t realize this circuit was on a separate fuse (I know- you don’t have to say it). It never occurred to me to check the fuse block, but sure enough, the fuse was blown.
2. The wire powering the electric choke is spliced in at the plug. When I changed to the HEI distributor, that wire got pinched between the distributor and the manifold, causing the short.

We’re back in business charging at almost 13v at idle.

Thanks again for all the help.

 

[DeanT]

My Bronco runs and starts fine, but the voltage is consistently low. It never gets to 12V, nor does it drop below 11.2ish. Very little change in voltage whether its running or not. I only noticed because I installed a USB outlet that has a volt meter built in. I confirmed voltage with a meter.

Any ideas what is causing this?

So far I've done the following trying to chase down the issue:
1. Replaced alternator.
2. Replaced Voltage Regulator
3. cleaned all contact points for battery ground wire.
4. Asked myself why I'm so concerned if it starts and runs every time I ask it to.

Battery tested good, but only had 11v. Truck has a Centech wiring harness.

There's no voltage drop-off after sitting for a week or two. Help me out, I'm stumped.

ECM,
I had an Interstate battery that developed an internal short some how. Started ran fine but, always acted like I was running it with everything on the truck ON. I installed a volt meter instead of the amp meter and it showed the same as my hand held meter. Took battery back to Interstate and they tested it to be good. Finally I but a battery in from my F-150, fixed it right up. Took the battery back argued with them till they did a 11/2 hour load test a that came back internally grounded. Installed the new battery works fine. I installed a PowerMaster 100 amp single wire made to bolt in perfectly and it did. No more external voltage regulator. I guy at PowerMaster told me a bad battery will damage your alternator.