Voltage regulator?

[Selahdoor]

It's the same guy who loaned me his meter. He doesn't loan that to ANYone! But he trusted me with it. Then got these for me, today.

 

[onetonjohn]

Good to have friends. Those tools should serve you well.

 

[Selahdoor]

What happens if you run the alternator with the three pin ASI disconnected?

Common sense says the alternator will put nothing out. But little of what you are seeing makes any sense to me. It can't happen, but it is.

With engine running, and both/either of the connectors disonnected, the alt puts out nothing at all, and the battery light comes on and stays on, on the dash.



I have now tested all the meters.

My new meters are in perfect sync with my friend's meter. And with each other, of course.

Also my analog meter is in sync with them. But the dial is so tiny on that, that it is all but worthless to me for this sort of thing. I can barely see the difference between 12v and 15volts. Let alone 12.6 and 14.2.

The HF multimeter was consistently high. But not consistent in ANY other way. You never know how much it is going to be off, or when. Etc.

It does, though, almost consistently read ~14.4volts AS 15.6 to 15.9 volts. Occasionally reading higher. And occasionally actually reading correct.

What it looks like at this point, is that the batteries were boiling because they were BAD batteries. Period. The alt was probably always working at 14.2 to 14.8 volts, while charging.

So, yeah, I have wasted a perfectly good alternator. But you know, I almost would do it all over again, just for the learning experience.

 

[Thewespaul]

Voltage is electrical pressure, if your batteries have a dead cell or two, they will resist charging. Think of this like a 100 gallon air compressor trying to bleed off all its volume through a tiny pinhole, its going to have a lot of airline pressure behind the pinhole as all the air trys to get out versus if it had a gaping hole in the reservoir, not much pressure there. Pressure is resistance to fluid flow in hydraulics, and if you have bad batteries or poor connections, that will resist the electrical flow into the batteries, making more electrical pressure, or voltage. Im not saying this is your complete issue, but I havent seen it mentioned in the thread before, and I think its worth mentioning as I see it cause all kinds of issues in these old trucks.

^

 

[Selahdoor]

Yep. I should unlike your post, just so's I can like it again.

 

[BeastMaster]

With engine running, and both/either of the connectors disonnected, the alt puts out nothing at all, and the battery light comes on and stays on, on the dash.

That puts to bed any thoughts I was entertaining about an internal short in the alternator making it put out even if none was called for.

I am puzzled why the battery light came on. Disconnecting the I wire should have depowered it.

What it looks like at this point, is that the batteries were boiling because they were BAD batteries. Period. The alt was probably always working at 14.2 to 14.8 volts, while charging.

If you had a shorted cell in each of your batteries, yes, the remaining five cells would experience severe overcharging.

But you were reading so much overvoltage. All the classic symptoms of a bad voltage regulator.

So, yeah, I have wasted a perfectly good alternator. But you know, I almost would do it all over again, just for the learning experience.

This is the seasoning that separate the men from the boys. Every technical person worth their salt gets their training the same way.

Funny thing though, once we have been through enough of this to be aware of some of the pitfalls out there, the business community considers us too old...

 

[Selahdoor]

That puts to bed any thoughts I was entertaining about an internal short in the alternator making it put out even if none was called for.

I am puzzled why the battery light came on. Disconnecting the I wire should have depowered it.

Ok, you got me there.

It came on when the small grey connector was disconnected.

I didn't check the dash again, with the larger connector disconnected.

Wait. Yes I did, and yes it did.

I'm done for the day. I'm not going back out there to check tonight.

 

[BeastMaster]

Franklin2 posted this on page 4

https://www.oilburners.net/attachments/af69710d-8dff-4985-bf1f-55e708fcf0fb-jpeg.124143/

Trace the battery indicator light circuit to see the root of my confusion.

Looks to me like the regulator has to ground the I wire to light the indicator.