Scool Me In Wiring (5 Viewers)

[bj40green]

I posted the diagram just to explain that the SENSE wire has to be connected to the Battery and not to the B terminal on the alternator.
As I understand GM alternators.... They are activated by the L (Lamp = idiot light) from switched power.
They (sometimes) need a resistor or a diode in series.
Google for: GM 10SI or GM 12SI wiring diagram. Click on pictures and.... tadaaaa
https://www.google.com/search?q=gm 10si alternator wiring&rlz=1C1CHHJ_enCR399&espv=2&biw=1280&bih=649&source=lnms&tbm=isch&sa=X&ei=shyVVN-ZM8P2ggSapYTABg&ved=0CAYQ_AUoAQ#tbm=isch&q=gm 10si alternator wiring
or
https://www.google.com/search?q=gm 10si alternator wiring&rlz=1C1CHHJ_enCR399&espv=2&biw=1280&bih=649&source=lnms&tbm=isch&sa=X&ei=shyVVN-ZM8P2ggSapYTABg&ved=0CAYQ_AUoAQ#tbm=isch&q=gm 12si alternator wiring

HTH,
Rudi

 

[RWBeringer4x4]

Bj40green posted a diagram for, I believe a 3 wire alternator, if you truly have a 1 wire GM unit, the the 1 wire would just go to either the battery OR the main wire to the fuse box or dist block. The other wires are for the charge light.
MAD Electronics has some good info, actually after reading it you'll probably want to go with a 3 wire GM setup... I did. The advantage of the 3 wire is that the sensing wire can be at the fuse block and the charge wire can be at the batt. With a 1 wire set up, like you have the sensing wire and charge wire are the same.

Hey Nick -

I think I've discovered that I DO NOT have a one wire alternator, I have an externally regulated alternator with none of the regulator wires hooked up - which is a problem.

I've read about the one wire vs. 3 wire setups, and 3 wire is definitely where I want to end up.

I posted the diagram just to explain that the SENSE wire has to be connected to the Battery and not to the B terminal on the alternator.
As I understand GM alternators.... They are activated by the L (Lamp = idiot light) from switched power.
They (sometimes) need a resistor or a diode in series.
Google for: GM 10SI or GM 12SI wiring diagram. Click on pictures and.... tadaaaa
https://www.google.com/search?q=gm 10si alternator wiring&rlz=1C1CHHJ_enCR399&espv=2&biw=1280&bih=649&source=lnms&tbm=isch&sa=X&ei=shyVVN-ZM8P2ggSapYTABg&ved=0CAYQ_AUoAQ#tbm=isch&q=gm 10si alternator wiring
or
https://www.google.com/search?q=gm 10si alternator wiring&rlz=1C1CHHJ_enCR399&espv=2&biw=1280&bih=649&source=lnms&tbm=isch&sa=X&ei=shyVVN-ZM8P2ggSapYTABg&ved=0CAYQ_AUoAQ#tbm=isch&q=gm 12si alternator wiring

HTH,
Rudi

Yeah - I've actually seen both those sites (and about 100 others) in my own Google searching. The problem is that there is a lot of information (and misinformation) out there. Every time I think I have it figured out I find another site entirely contradicting the last...

Bottom line - I trust you guys more than the rest of the Internet - so I appreciate all the feedback!

In terms of the sense wire - all the reading I did last night points in the same direction, it needs to be hooked up, and run through a resistor if you're not using a warning light...

I need to trace the brown wire on my voltage regulator and see where it runs...it traced it up into the dash but that's where I stopped looking.

 

[Vae Victus]

Wow. Can o Worms Rick! Subd to watch & learn.

 

[Pin_Head]

Just remember when you read web sites that many of them are trying to sell you solutions to things that the factory engineers didn't consider to be problems.

 

[RWBeringer4x4]

Wow. Can o Worms Rick! Subd to watch & learn.

I don't think it is as bad as it looks - it's dangerous, as it is, but the "dangerous" part is easily repaired. Most of the questionable wiring is the alternator, not the stock harness...the stock harness just has a ton of unplugged plugs I need to decipher - my guess is most of them relate to the (long gone) smog controls.

Just remember when you read web sites that many of them are trying to sell you solutions to things that the factory engineers didn't consider to be problems.

Agreed - though when it comes to a 3 wire alternator, they make a lot of good points.

 

[bj40green]

Does this diagram match your situation?

Rudi

 

[RWBeringer4x4]

Does this diagram match your situation?
View attachment 1007357

Rudi

That exactly matches my setup. Except that the "F" and "2" terminals are currently disconnected at the alternator.

The "3" terminal hooks directly to the battery, not the alternator.

 

[bj40green]

That exactly matches my setup. Except that the "F" and "2" terminals are currently disconnected at the alternator.

The "3" terminal hooks directly to the battery, not the alternator.

The "3" should be hooked up to the battery with a fusible link is series like this.

So, hook up, start engine and see what happens.

Rudi

 

[RWBeringer4x4]

The "3" should be hooked up to the battery with a fusible link is series like this.
View attachment 1007382

So, hook up, start engine and see what happens.

Rudi

That's the plan, unfortunately the connector on the wire to terminal 3 corroded and cracked (and missing a fusible link) so it will need to be rebuilt. Once that's replaced and connected, I'll plug the "F" and "2" terminals in at the alternator and see what happens.

If it is charging and regulating properly, I'll just run it. If it was unplugged for a reason, I'll probably ditch the external regulator and go to an internally regulated system - that was where all the questions about internally regulated alternators were coming from.

 

[RWBeringer4x4]

Alright folks, I'm back -

Started running some voltage tests tonight, and they leave me even more confused than usual.

I repaired the wire that had broken previously at the voltage regulator, cleaned off the voltage regulator's contacts, and hooked it back up. FYI - here it the regulator. It has "Toyota" hand-written on it, but it looks GM to me...

I tested the voltage across the terminals at the battery while it was sitting (no lights on, no key in the ignition) - the batter read 12.2 volts - seems about right?

Here is where it gets confusing. I fired up the truck, and the voltage immediately DROPPED to 11.9, and stayed there. The picture below is with the engine running:

If you turn the headlight on, voltage drops to 11.7, but even after a few minutes at idle, it appears to stay constant at either of these numbers. It doesn't continue to drop, as if the battery is completely de-charging. It sits at a constant 11.7 with the lights on and engine running.

Next, I tested it at the alternator, between the main battery stud, and the ground cable to the fender. The results - virtually identical:

In the cab, the amp meter stays consistently pegged at in the center of the gauge, between +30 and -30. It drops toward -30 as accessories are turned on, and returns to center when turned off. You can see it move back and forth with the blinkers, so it appears to be working...However, it never goes ABOVE the center line, as if it were charging.

What's also weird, is that revving the engine seems to cause the voltage to DROP slightly both at the battery and at the alternator. The current actually reduces about 0.2 volts. I would have thought volt output would INCREASE as the engine revs, particularly when making a raw, unregulated reading at the alternator...

Note: Nothing changes, with the voltage regulator plugged in, unplugged, etc.

Voltage returns to ~12-12.2V when the engine is shut down.

My only theory? The alternator is half dead, providing a constant, unregulated 12 volts to the battery, which is just enough to keep it from dying. Otherwise, I imagine it would have died in the couple hundred miles I've put on it. Given that it was showing 12 volts, even after sitting in a cold garage for the past 3 months, seems to suggest it's being charged...Am I close? Does this make any sense?

 

[71FJnick]

Might be worth pulling the alternator and having it bench tested at autozone or napa for free. That may help eliminate 1 component from the equation.
If the alt is bad then you could justify the upgrade to an internally regulated version, if it's good, then maybe you just need a regulator.

 

[RWBeringer4x4]

Might be worth pulling the alternator and having it bench tested at autozone or napa for free. That may help eliminate 1 component from the equation.
If the alt is bad then you could justify the upgrade to an internally regulated version, if it's good, then maybe you just need a regulator.

Will they bech-test an externally regulated alternator? I thought they only did modern, internally regulated ones. I guess thats a better question for them, though.

 

[71FJnick]

Ah you may be right. Napa may do the old ones... They seem to have more knowledge with older stuff

 

[bj40green]

RWBeringer4x4 wrote:

I tested the voltage across the terminals at the battery while it was sitting (no lights on, no key in the ignition) - the batter read 12.2 volts - seems about right?
That's a nice voltage. No problem here.

Here is where it gets confusing. I fired up the truck, and the voltage immediately DROPPED to 11.9, and stayed there. The picture below is with the engine running
That's normal because the gauge cluster and the ignition circuit are a load to the battery. No problem here.

If you turn the headlight on, voltage drops to 11.7, but even after a few minutes at idle, it appears to stay constant at either of these numbers. It doesn't continue to drop, as if the battery is completely de-charging. It sits at a constant 11.7 with the lights on and engine running.
This is also normal. More load to the battery is a little voltage drop. No problem here.

Next, I tested it at the alternator, between the main battery stud, and the ground cable to the fender. The results - virtually identical:
View attachment 1011250
You're measuring the voltage from the battery because the alternator is not charging. And that is the problem. The question is why????

In the cab, the amp meter stays consistently pegged at in the center of the gauge, between +30 and -30. It drops toward -30 as accessories are turned on, and returns to center when turned off. You can see it move back and forth with the blinkers, so it appears to be working...However, it never goes ABOVE the center line, as if it were charging.
Normal behavior because the alternator is not charging.

What's also weird, is that revving the engine seems to cause the voltage to DROP slightly both at the battery and at the alternator. The current actually reduces about 0.2 volts. I would have thought volt output would INCREASE as the engine revs, particularly when making a raw, unregulated reading at the alternator...
Normal behavior because the current draw in the ignition circuit changes a tiny bit.

Note: Nothing changes, with the voltage regulator plugged in, unplugged, etc.
Voltage Regulator or Alternator defective! You've to figure out which one.

Voltage returns to ~12-12.2V when the engine is shut down.
Good!

My only theory? The alternator is half dead, providing a constant, unregulated 12 volts to the battery, which is just enough to keep it from dying. Otherwise, I imagine it would have died in the couple hundred miles I've put on it. Given that it was showing 12 volts, even after sitting in a cold garage for the past 3 months, seems to suggest it's being charged...Am I close? Does this make any sense?
Nope. The alternator is not giving output. What you see is the battery voltage.

Here is a way to check if the alternator is working.
- unplug the Voltage Regulator.
- prepare a piece of wire.
- start engine
- hook up volt meter to the battery
- take that piece of wire and hook it up to the + stud battery
- take the other end and hold it against the F terminal on the alternator
- watch your volt meter
- rev up the engine a little bit to, say 1000 rpm
- read the voltmeter..... does it go up? VR is defective or you have a wiring problem in the VR circuit. Does the VR (on the IGN terminal) get 12V from the ignition key?
- read the voltmeter..... no change? Alternator defective.

Rudi

NOTE: Don't rev up the rpm's too high. The alternator output is not controlled and depends now purely on the rpm's.

 

[RWBeringer4x4]

RWBeringer4x4 wrote:

I tested the voltage across the terminals at the battery while it was sitting (no lights on, no key in the ignition) - the batter read 12.2 volts - seems about right?
That's a nice voltage. No problem here.

Here is where it gets confusing. I fired up the truck, and the voltage immediately DROPPED to 11.9, and stayed there. The picture below is with the engine running
That's normal because the gauge cluster and the ignition circuit are a load to the battery. No problem here.

If you turn the headlight on, voltage drops to 11.7, but even after a few minutes at idle, it appears to stay constant at either of these numbers. It doesn't continue to drop, as if the battery is completely de-charging. It sits at a constant 11.7 with the lights on and engine running.
This is also normal. More load to the battery is a little voltage drop. No problem here.

Next, I tested it at the alternator, between the main battery stud, and the ground cable to the fender. The results - virtually identical:
View attachment 1011250
You're measuring the voltage from the battery because the alternator is not charging. And that is the problem. The question is why????

In the cab, the amp meter stays consistently pegged at in the center of the gauge, between +30 and -30. It drops toward -30 as accessories are turned on, and returns to center when turned off. You can see it move back and forth with the blinkers, so it appears to be working...However, it never goes ABOVE the center line, as if it were charging.
Normal behavior because the alternator is not charging.

What's also weird, is that revving the engine seems to cause the voltage to DROP slightly both at the battery and at the alternator. The current actually reduces about 0.2 volts. I would have thought volt output would INCREASE as the engine revs, particularly when making a raw, unregulated reading at the alternator...
Normal behavior because the current draw in the ignition circuit changes a tiny bit.

Note: Nothing changes, with the voltage regulator plugged in, unplugged, etc.
Voltage Regulator or Alternator defective! You've to figure out which one.

Voltage returns to ~12-12.2V when the engine is shut down.
Good!

My only theory? The alternator is half dead, providing a constant, unregulated 12 volts to the battery, which is just enough to keep it from dying. Otherwise, I imagine it would have died in the couple hundred miles I've put on it. Given that it was showing 12 volts, even after sitting in a cold garage for the past 3 months, seems to suggest it's being charged...Am I close? Does this make any sense?
Nope. The alternator is not giving output. What you see is the battery voltage.

Here is a way to check if the alternator is working.
- unplug the Voltage Regulator.
- prepare a piece of wire.
- start engine
- hook up volt meter to the battery
- take that piece of wire and hook it up to the + stud battery
- take the other end and hold it against the F terminal on the alternator
- watch your volt meter
- rev up the engine a little bit to, say 1000 rpm
- read the voltmeter..... does it go up? VR is defective
- read the voltmeter..... no change? Alternator defective.

Rudi

@bj40green - Rudi, fundementally, I agree with all of the above, EXCEPT - if my alternator is not charging, why hasn't my battery died? I've driven the truck around quite a bit, including a 40+ minute drive at one point. I imagine the battery would drain fairly quickly - not provide a solid 12.2 volts, if the alternator was not charging at all...

Also - The voltage regulator was unplugged when I measured the voltage at the alternator, so it shouldn't have been "regulating" the alternator current. With the regulator unplugged, shouldn't the voltage at the alternator read true to the alternator, and fluctuate with engine RPM?

It seems entirely possible to me that BOTH might be defective, given that I get the same performance whether the voltage regulator is plugged in, or not...

I still don't understand why my battery isn't dying though...

 

[bj40green]

If your VR is disconnected, there is no way that there is output from the alternator.
Correction; unless somebody "modified" (f*cked up) the internals of the alternator into a 1 wire alternator and that's the reason why the VR was disconnected.
In that case you're probably looking at one or more defective rectifier diode's inside the alternator.

BTW... you can drive for hours on your battery if it is in a good condition.

Rudi

 

[RWBeringer4x4]

Is converting an alternators internals to a 1-wire setup common? Even so, wouldn't I be seeing voltage around 14v at both the alterantor and the battery when the truck was turned on? Would a bad rectifier diode provide SOME charge (say, 11.9 volts) but not a full 14 volts?

They're just giant spinning mystery boxes to me!

 

[bj40green]

Is converting an alternators internals to a 1-wire setup common? Even so, wouldn't I be seeing voltage around 14v at both the alterantor and the battery when the truck was turned on? Would a bad rectifier diode provide SOME charge (say, 11.9 volts) but not a full 14 volts?

They're just giant spinning mystery boxes to me!

No, modifying the internals is not common but people can do the strangest things.
If they did so, then where is the regulator?
Maybe they blew up the diode's because of that.
Who knows?

I've seen in my life the strangest things when people "repaired" their apparatus.
Lubricating the drive mechanism of a cassette player with olive oil.
Bending the tape guides on a VCR straight. They should be under an angle to guide the tape around the head.
Cutting a hole in the black grill/grate on the back of a refrigerator to fit it over a wall outlet. And there goes all the freon!
I can tell a few hundred more stories.
When confronted with their "repairs" the owners had always a nice excuse... My neighbor did that. He's so handy he works at Shell, KLM, Fokker, IBM, and so on.

Anyway.... we have the chicken and the egg situation here.
Voltage Regulator, alternator or both are defective.

If you really want to test the alternator before you take it to NAPA.....
Disconnect the +B wire from the alternator, isolate it (it's live with the battery voltage) and do the test I described above.
This will tell if there is any voltage coming out of the alternator. The volt meter of course now hooked up to the +B on the alternator.

Rudi

 

[RWBeringer4x4]

Ok - and the next question: If I go to a "modern" internally regulated alternator - they tend to be higher output. The current alternated is rated at 63amps, when it's working. I'd like to get a little bit more "juice" but I have also read that you can overload the stock amp-meter/wiring with a high-output alternator.

My understanding is that alternators only put out amperage "on-demand," so as long as there is a proper load on the system - i.e.: whatever accessory you are running, it shouldn't be overloading anything.

It seems this forum has gone back and forth on this - some people running 100amps on stock wiring/gauges with no problems, others saying this is a wire-fire waiting to happen. Is there a definite "right" answer to this? I'm not going to run out and buy the biggest, nastiest alternator I can find, but given that I'm upgrading to Halogen lights and probably going to have a few additional accessories (some day) it might be worth thinking ahead.

 

[bj40green]

It's pretty easy.
Take off the WL (White/Light Blue stripe) wire from the +B stud on the alternator. Isolate it.
Run a new wire/cable with a fusible link from the +B stud on the alternator to the battery.
This way the Ammeter only shows the current draw on the OEM wiring harness and not the charge current.

Add a new fuse block to the + battery stud and go from there for your fog lights etc.
Install a Volt meter or maybe the new alternator comes with a charge light.

Rudi