Voltage regulator?

The_Josh_Bear

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With 15v output, there’s nothing wrong with the alternator, the regulator is the problem. You’ve still got some life in those brushes.
+1

Also, brushes typically come with the regulator assembly so getting both is easy. (But make sure they do, some are sold as reg only)
No need to find a rebuild kit unless you have iffy bearings or other issues outside of the regulator.
 

BeastMaster

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I was looking at the wiring diagrams... The regulator has a three pin connector, pins labeled "A", "S", and "I".

A is the power to the armature. It is connected to the main battery buss, same as the main alternator output. The regulator will gate current from this line through the brushes and energize the armature rotor winding to create it's magnetic field should this voltage be less than 14 volts or so. Set by design. This voltage is referenced to the alternator frame ground. Armature current is also returned to the alternator frame ground.

Should the connection to A be open, there will be no armature drive current available, no magnetic field, no output.

However, should that connection be lossy, and you are losing, say, 4 volts across a corroded connection, the regulator will call for more and more voltage, increasing armature drive current, until it sees the 14 volts it's looking for. But the alternator is actually putting out 18 volts to get that 14 volts at the regulator sense point.

The S terminal is an alternator sense point. It's connected to one of the three legs of raw three phase AC power coming from the stator winding. It let's the regulator know the alternator is turning.

It's that wire that loops from the regulator connector right back to a single small connector pin on the main alternator body.

Not much sense giving armature current to an alternator that's not spinning. All that will do is drain the battery.

The I terminal just drives an indicator lamp if something's wrong, by pulling the line to ground.

I note you have already looked carefully at the grounding...which is probably the most common gremlin in the fray.

Hope this gives you a little more info to work with.

At this point, I agree that you have a bad voltage regulator, with my belief that inside it is a shorted pass transistor for armature field current.
 
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Selahdoor

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Going to get some work done today.

Ok, so here is where we are at, today.

Took the alternator in for testing yesterday.


First place I stopped at. A local parts shop. They didn't have the right connector for this alternator. Couldn't test it.

Napa. Tester is not working.



O-reilley's. Took the guy more than half an hour to figure out how to hook the alternator up. No. I'm not kidding. More than half an hour. And he never got it right. I could tell just from looking at it. But he wasn't listening, so I wasn't suggesting...

First two tests, no results. Last two tests, fail. I caught him just before he deleted the screen, the last time, and asked him WHY it failed. After looking at the screen... "I don't know".

Then I asked, well what voltage is it putting out? He peered at the screen for a bit. Then changed to the next page of the screen. Then said 10 volts. I asked him if he was sure. He said yes, and pointed at the screen where it said 10 volts, with a big grin, and chest stuck out, proud that he had found it and could point at it on the screen. LOL



I decided to go to the last place in town. Autozone.

Guy had it hooked up in less than three minutes. And that included having to get out the special mounting pieces, and put them together.

Tested three times. All three times, green lights all the way. Absolutely nothing wrong with the alternator.

I trust this test, because I saw the ease, thoroughness and professionalism he had, in testing it. And because if anything he would have incentive to make sure it failed, so they could sell me an alternator...


Which MAY confirm what I suspected. That the alternator and voltage regulator are ok. Either the gauge, or the wiring has a problem that is causing the wrong voltage/amperage/signal to get back to the alternator.

Now I have to figure out what could do this.


But before anything else, in a little while, I will get out there, replace the alternator correctly, and do the tests on the regulator itself, that you can do while it is on the running engine.

That will begin later today. I wanted to post this, to get feedback. What do you think?

Ideas about the wiring?

Thanks to BeastMaster for the info about the gauge. As far as the gauge is concerned, I am convinced that it is reading wrong. It is reading about 3 to 4 volts higher than it should. But... the alternator IS still overcharging. Maybe the gauge is itself, the problem? (Meaning, it reads wrong, but it is also causing the problem with the actual high charge?) I'm wondering how I would bypass that, to find out if that is the problem?
 
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renjaminfrankln

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Are you using the factory gauge on the truck? Using those gauges for anything is worthless

Mine reads anywhere from 9-13v on the factory gauge depending on how its feeling, yet the truck is consistently at 14v when measured. I put a $10 USB charger with a voltage readout in my cigarette lighter so I can keep an eye on it.
 

Selahdoor

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Are you using the factory gauge on the truck? Using those gauges for anything is worthless

Mine reads anywhere from 9-13v on the factory gauge depending on how its feeling, yet the truck is consistently at 14v when measured. I put a $10 USB charger with a voltage readout in my cigarette lighter so I can keep an eye on it.
Yes. Factory gauge.

As I have already pointed out, I believe the gauge is inaccurate.

I am not looking at the gauge, and going, "oh my gosh! The alternator is overcharging!" LOL

I measured the voltage at the battery while it was charging. And the voltage was 15.61. That... is overcharging. Read by a voltmeter at the battery...


I am sure the gauge is inaccurate. (While the voltmeter at the battery read 15.61, the factory gauge was reading 18v. That, alone is proof the gauge is inaccurate.)

What I need to know is.. Can the gauge itself be the CAUSE of the overcharge?

And, how do you bypass the gauge to test with the gauge out of the circuit? (Meaning, do I just disconnect the gauge, and get on with it? Or do I have to jumper the wires that go to the gauge? Etc...)

I like the idea of using that USB charger in, to keep track of the voltage. I have had in the back of my head, a bit different idea. Hang my voltmeter from the dash bezel. Meantime, take the wires off the factory gauge, and connect them to my voltmeter instead, and have a more accurate volt readout. Again, just need to know
 

Reggie f250

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The voltmeter in dash only samples voltage in the instrument panel, nothing else. Just the same as you checking voltage at the battery.
 

franklin2

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I was looking at the wiring diagrams... The regulator has a three pin connector, pins labeled "A", "S", and "I".

A is the power to the armature. It is connected to the main battery buss, same as the main alternator output. The regulator will gate current from this line through the brushes and energize the armature rotor winding to create it's magnetic field should this voltage be less than 14 volts or so. Set by design. This voltage is referenced to the alternator frame ground. Armature current is also returned to the alternator frame ground.

Should the connection to A be open, there will be no armature drive current available, no magnetic field, no output.

However, should that connection be lossy, and you are losing, say, 4 volts across a corroded connection, the regulator will call for more and more voltage, increasing armature drive current, until it sees the 14 volts it's looking for. But the alternator is actually putting out 18 volts to get that 14 volts at the regulator sense point.

The S terminal is an alternator sense point. It's connected to one of the three legs of raw three phase AC power coming from the stator winding. It let's the regulator know the alternator is turning.

It's that wire that loops from the regulator connector right back to a single small connector pin on the main alternator body.

Not much sense giving armature current to an alternator that's not spinning. All that will do is drain the battery.

The I terminal just drives an indicator lamp if something's wrong, by pulling the line to ground.

I note you have already looked carefully at the grounding...which is probably the most common gremlin in the fray.

Hope this gives you a little more info to work with.

At this point, I agree that you have a bad voltage regulator, with my belief that inside it is a shorted pass transistor for armature field current.

You have got the "A" terminal and the "S" terminal backwards. As you can see in the diagram below, the "A" terminal goes to the regulator, it's the sensing wire to sense voltage levels in the wiring harness.

The "S" terminal is the stator terminal. It goes directly to the stationary windings on the outside of the alternator.

On alternators, what you would normally call the "armature" or part that is turning, is actually the field windings. So they control the output of the alternator by varying the magnetic field of the piece that is turning in the middle. This is why it generates a A/C voltage, 3 phase actually, and why it needs all those diodes to convert it to DC so we can use it to charge the battery and run all the DC stuff in the truck.


af69710d-8dff-4985-bf1f-55e708fcf0fb-jpeg.124143
 

BeastMaster

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Thanks, Frank!

I think the confusion is in how I am interpreting and assigning labels.

I see terminal "A" as the power terminal to feed current into the armature rotor to establish a magnetic field. This same line is also sensed by the voltage regulator, which gates this voltage, or some of it, to the armature through the brushes, if the voltage is below the 14 volts setpoint.

However, in the event the engine is not running, and the stator is not developing sufficient voltage to do any good, something has to tell the regulator to shut down the armature current. No sense feeding power and not get any.

This condition will exist if the engine is shut down or idling too slow to develop enough voltage to charge.

So, that is what the "S" connection is for. It sees a raw sample of the AC voltage being developed at the stator coil. If there is not enough voltage coming off the coil, it tells the regulator to shut down.

Note the alternator's three phase diodes keep the battery voltage from feeding this point. Any voltage here has to come from the stator coil.

I suspect Selahdor' s regulator is stuck on high, due to internal short in it's pass transistor. This will also cause a serious parasitic draw as his alternator will constantly have it's armature winding energized, regardless of the engine running or not.
 
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raydav

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When you get the issues settled I suggest a 3G alternator. It is a bolt on replacement. You can connect it as sorta one wire, or with two wires you can have a light.
 

Selahdoor

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Taking a break.

Made something to help with the testing. Guess what it is for.
You must be registered for see images attach



Ok, here's a hint.
You must be registered for see images attach




Alright, here it is, hooked up. Yeah, it's so I can test with the "F" connection. Where the alt sits, I don't want to climb all the way up there, with my fat gut, (and beard), hanging over the fan, while I fumble around with a test lead on the back of the alternator hoping I am touching that "F" screw. So I made this, and bolted it down with the "F" screw.
You must be registered for see images attach



Now, here is the alternator, back on the engine, with that test lead sticking up.
You must be registered for see images attach



Now for the next stupid question.

I can see the test instructions all over the place. But I can't see one simple question answered, ever...

When you do the tests, where you touch the "F" terminal for ground, then touch each of the other connections with the red lead, while it's running... Do you disconnect the connector, and touch the metal blades inside, on the alternator? Or do you leave them connected and probe down beside the wires?
 

BeastMaster

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When you do the tests, where you touch the "F" terminal for ground,
Touching that F terminal to ground should turn the alternator full ON. Typically used for seeing if a dead regulator or a dead alternator is the culprit of a no-charge situation. I am pretty damm sure your alternator is fine.

Since you've made a nice test point there, measure the voltage from the F terminal to ground. It oughta go to battery voltage if the engine is OFF. Upon engine start, it should drop LOW until battery buss voltage gets up to 14V, then start rising as the regulator starts throttling the alternator back down.

With the engine OFF, do you have battery voltage at BOTH the F and A screw?

That is an interesting tale of woe bringing a technical problem to a business. Its the same in my field too. Once we have a technically viable work team, we generate enough cash flow to hire the bean counter that lays us all off to generate executive performance bonuses. While the guys who actually did the work languish in the welfare lines.
 
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Selahdoor

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Touching that F terminal to ground should turn the alternator full ON. Typically used for seeing if a dead regulator or a dead alternator is the culprit of a no-charge situation. I am pretty damm sure your alternator is fine.

Since you've made a nice test point there, measure the voltage from the F terminal to ground. It oughta go to battery voltage if the engine is OFF. Upon engine start, it should drop LOW until battery buss voltage gets up to 14V, then start rising as the regulator starts throttling the alternator back down.

With the engine OFF, do you have battery voltage at BOTH the F and A screw?
Yes. Full battery voltage at each of the two screws, with the engine off.
 
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