Voltage issue

[BobbyA]

Been having voltage issues for the past few months. 71 bronco with mustang EFI. Just replaced battery 6 months ago, tested alternator and it passed , new voltage regulator.

Measured voltage at battery with engine off, at 12 volts. Before replacing regulator while running, it was just above 13volts. Replaced regulator with new electronic one. Fired right up at idle and was at 14.46.
Took for a test drive and was fine until I noticed it quite wasn’t running well. Stopped and truck died. Slow crank but finally started again. Got it home and idled it and voltage was down again to 13 while idling. Did regulator get fried? Something else I should check on?

 

[DirtDonk]

Yes, fire the engine up again and measure the voltage above idle.
If it goes back up to the 14 V range when you get it above idle, then it might be working as designed.
Well, not optimally maybe. But at least similar to how lot of them worked back then.

Do you keep an eye on your ammeter? Or has it been replaced by a voltmeter?
At the very least you should get a digital voltmeter to stick in the cigarette lighter as a temporary monitor.

 

[Johnnyb]

I may be off base here, but if you have Mustang EFI do you also have a 3G or 4G alternator?

 

[DirtDonk]

Good question!
If so, then the opposite of what I said. Any 3g or later alternator would easily (should easily) put out plenty of power even at idle speeds.
It's just the older 1g units that had that problem sometimes. Usually only when they were well worn and getting on in years, but some had the issue right out of the box.
Not a really big problem if you are driving it more and idling it less, but it's something to be aware of at least. I never had that problem with any of my 1G units, but plenty have reported it.

Paul

 

[Johnnyb]

I was thinking more along the lines of: with a 3G or 4G alternator why would there even be a voltage regulator?

 

[DirtDonk]

Oh, I see. I was originally just under the assumption that they had reused all the old standard bronco stuff on the front of the later model engine.
All good questions awaiting answers.

 

[Johnnyb]

Could very well be but I was wondering?

 

[BobbyA]

From what I can tell stock 1g alternator. Stock ammeter which is fluctuating and does get close to middle and volts at battery at idle is close to 13.0

 

[gr8scott]

All good questions awaiting answers.

Pictures work too...

 

[Broncobowsher]

If he replaced the regulator after having the alternator tested, that would be a 1G system. The rest of the options have the regulator built into the alternator and the alternator test would have included the regulator test at the same time.

We have a 6-month old battery. I have had new batteries die in that time with nothing else wrong
An alternator that was tested and passed.
A new regulator, and I suspect any new part as being bad with how bad the parts quality is these days.

I would get the battery tested.
Clean battery connections and grounds.
Then start testing the rest of the charging system.

 

[DirtDonk]

From what I can tell stock 1g alternator. Stock ammeter which is fluctuating and does get close to middle and volts at battery at idle is close to 13.0

That 13v at idle, as long as it goes up when the engine revs up, is not a voltage issue from the alternator.
You have something else going on.
Perhaps loose wiring or a dying battery.

Time for some more deep testing…