Alternator Question

[Wolf Fabrication]

My random Argentine alternator only charges above a certain RPM, around 1000 or so, so I assume it must be from some other vehicle. Wouldn't a normal alt charge at idle?

[James Pierce]

We had a similar issue with a scout alt. that would kick in and charge when revved up. I'm completely guessing here but it may be the hot wire that feeds the regulator or the regulator itself. Does it continue to charge once it kicks in or do you have to keep it revved up for it to charge?

[Wolf Fabrication]

It's so damn sporadic. The truck actually died today at the end of a test drive. So the alt doesn't know when to charge.

[D90user]

is it a generator or alternator?

[Wolf Fabrication]

is it a generator or alternator?

Alternator

[D90user]

gotcha... should work then :)

[aka rover]

Im having the same problem and mines an alt. It charges above 850-900 but at an idle at a stop sign it will start to disscharge. Its a GM type alt im thinking its just turning to slow at idle. It has a hand throttle so i bump it up in the winter or at night so it will charge in stop and go traffic. I have thought about a smaller pully to get it to spin faster?. Its a real pain and would like to fix it if possible.


Cheers Ed

[Wolf Fabrication]

Shoot, I think you are on to something I didn't catch. The alternator has the larger pulley swapped over from the generator, so it's likely spinning slower anyway.:hmm

[Red90]

Is it worth the hassle? Just get a proper alternator and pulley... It should charge at idle.

[Wolf Fabrication]

Is it worth the hassle? Just get a proper alternator and pulley... It should charge at idle.

No, hence the question. I'll be getting a new alt.

[o2batsea]

An alternator at idle will be putting out such a paltry few amps that it is virtually not charging at all. There are some diodes that are what they call "Low turn on" in that the alternator will begin charging at a much lower RPM. It isn't unusual that you aren't seeing any amps below 1000.

[Wolf Fabrication]

An alternator at idle will be putting out such a paltry few amps that it is virtually not charging at all. There are some diodes that are what they call "Low turn on" in that the alternator will begin charging at a much lower RPM. It isn't unusual that you aren't seeing any amps below 1000.

Understood, but by that logic the motor is running off the battery, which doesn't make sense in a low RPM truck that could spend much of it's life off road below 1000 rpm.

Either way, the alt is intermittently charging.

[James Pierce]

What flavor and model number is it? The alt. that is.

[Wolf Fabrication]

What flavor and model number is it? The alt. that is.

No clue. Argentine special!

[o2batsea]

Understood, but by that logic the motor is running off the battery, which doesn't make sense in a low RPM truck that could spend much of it's life off road below 1000 rpm.

Either way, the alt is intermittently charging.

It's not "logic" it's the way it is, no matter what alternator you have. Yes, alternators do charge intermittently. The alternator voltage sense wire is connected to the battery to determine the battery's voltage (or state of charge if you will). The alternator voltage regulator turns on the alternator output based on a factory low set point, usually somewhere around 13 volts.
Once the VR turns on the output the alternator will charge as much as it possibly can given a particular RPM. When the battery voltage once again reaches the high set point the alternator will turn itself off. The engine could be revving at 4000 rpm and the alternator will not be charging. This kind of VR is "dumb" in that it's power output curve is linear. There are external VRs that are "smart" in that they provide stepped increments of battery charge voltage based on the battery state of charge. That is, bulk charge, absorption charge, and float charge (there's a fourth charge rate called equalization that an alternator can't really handle).

If your battery is at, say, 14.4 volts at idle, then the alternator is not going to put out any charge current because the battery is full.
Hope that makes sense to you.

If anything, your alternator's VR is bad, but since you say it does put out charge, it is probably not that.

[Wolf Fabrication]

It puts out a charge, but is intermittent for some reason. At idle, it won't charge, but when I rev the motor it does. Then when I drive the truck it starts to run off the battery.

I still disagree that a motor idling is running off the battery (my logic point), as a motor is supposed to run by itself if you disconnect the battery. Am I off base on that? I've always diagnosed engine electrics that way.

[Red90]

An alternator at idle will be putting out such a paltry few amps that it is virtually not charging at all. There are some diodes that are what they call "Low turn on" in that the alternator will begin charging at a much lower RPM. It isn't unusual that you aren't seeing any amps below 1000.

BS. My stock 200TDI alternator gives a solid 13.5 volts at idle with the lights on and heater on full. I have a dash mounted digital gauge and know how the alternator is performing all of the time.

[Wolf Fabrication]

Just went out to the garage and checked the system again. It won't charge at idle, and when I rev the motor I get about 13v if I'm lucky. When I disconnect the battery the truck dies. In old skool auto mechanics this points to the alt as the culprit. The VR is an Echlin VR-32 and is new.

[Ren Ching]

On a vehicle with an alternator, don't disconnect the battery while the engine is running. You can fry the diodes in the alternator as there will be no sense voltage and the alternator can run up the voltage pretty quickly.

Sounds like you need a new one. And, a proper sized pulley. I have some extra pulleys here if you need one but they are available elsewhere.


Just went out to the garage and checked the system again. It won't charge at idle, and when I rev the motor I get about 13v if I'm lucky. When I disconnect the battery the truck dies. In old skool auto mechanics this points to the alt as the culprit. The VR is an Echlin VR-32 and is new.

[o2batsea]

On a vehicle with an alternator, don't disconnect the battery while the engine is running. You can fry the diodes in the alternator as there will be no sense voltage and the alternator can run up the voltage pretty quickly.

like in less than half a second. There is such a thing as a "zap stop" for knuckle heads who do that or have a 1,2,BOTH,OFF switch and turn it to off when the engine is running.

------ Follow up post added December 6th, 2011 01:04 PM ------

BS. My stock 200TDI alternator gives a solid 13.5 volts at idle with the lights on and heater on full. I have a dash mounted digital gauge and know how the alternator is performing all of the time.

Your battery should be reading 14.2-14.4 when the alternator is actually producing current. At 13.5 it's doing zippo. That's resting voltage for a fully charged battery. In addition a dash mounted gauge will be suffering some amount of voltage drop due to the wire resistance. Only when you put a multimeter across the battery terminals will you get a proper reading.

[Wolf Fabrication]

Urban legend boys. In principle, you would think, but it's a pretty common diagnosis tool. My alt didn't do shite when I disconnected it.

Been taking readings at the battery.

We can debate all day, either way I am getting a new alt.

[Ren Ching]

Urban legend boys.

Says the guy with the fubared alternator.

[Wolf Fabrication]

Here's the offender. Mounting tabs look wider apart than the correct RTC5083 Alernator.

[Red90]

Your battery should be reading 14.2-14.4 when the alternator is actually producing current. At 13.5 it's doing zippo. That's resting voltage for a fully charged battery. In addition a dash mounted gauge will be suffering some amount of voltage drop due to the wire resistance. Only when you put a multimeter across the battery terminals will you get a proper reading.

Wrong again.

12.7 is the battery voltage with no charging happening AND fully charged. Any voltage above that and the battery is charging. 14.2 Volts is the alternator control point and it will do that when possible.

My gauge is wired directly to the battery.......

[Ren Ching]

Correct for what?

Here's the offender. Mounting tabs look wider apart than the correct RTC5083 Alernator.

[Wolf Fabrication]

Correct for what? The upgrade to alternator from the genny on early Series trucks, or so sez RN and RDS.

At this point I don't care what goes in the truck, it just needs to fit and charge. Truck is sold....

[Ren Ching]

Cool. I did not know there was an option like that for the series 1 motors.

[Wolf Fabrication]

Cool. I did not know there was an option like that for the series 1 motors.

Not really an option per se, you have to fab up some brackets. Although the LR one is different from my Argentine special, so I'll have to make it work.

[o2batsea]

Wrong again.

12.7 is the battery voltage with no charging happening AND fully charged. Any voltage above that and the battery is charging. 14.2 Volts is the alternator control point and it will do that when possible.

My gauge is wired directly to the battery.......

Yo dat shiz'dope yo!

[Antichrist]

I still disagree that a motor idling is running off the battery (my logic point), as a motor is supposed to run by itself if you disconnect the battery. Am I off base on that? I've always diagnosed engine electrics that way.If you've done any diagnosis on this engine doing that then the likely problem is your alternator, you've probably fried the diodes.
Disconnecting the battery on a generator equipped vehicle (while the engine is running) is ok, but should never be done on an alternator equipped one.

I see Ren beat me too it, but apparently it bears repeating as it's not urban legend.

For a Series that still has the generator brackets, the easiest conversion is an AC Delco 10si
http://www.lrfaq.org/Series/FAQ.S.alt_alternators.html

[Wolf Fabrication]

Got it. Regardless, I've done it tons of times on old cars with no issue and didn't fry anything. I've never let the car run without the battery for more than a spilt second and never saw a spike in voltage from an out of control alternator. But I concede your point. Maybe I've just been one of the "lucky" ones.

I'm good on bracketry.

[Wolf Fabrication]

Got the new LR alternator. On the back it has two terminals sharing a +, and one marked IND. What's IND? Field? Or is this a true one wire internally regulated alternator?

[Wolf Fabrication]

Hmmm. IND appears to be indicator light.

------ Follow up post added December 8th, 2011 06:47 PM ------

...and I no longer need a voltage regulator?

[Red90]

It is for the battery light wire. That accepts the standard alternator connector. They are available in the UK for a couple of bucks. Voltage regulator is built in. I've got a few at home if you want one.

edit: here - http://www.autosparks.co.uk/product_info.php?products_id=1218

How exactly is your truck wired up now? Having the correct battery light wiring is essential for the alternator to work. This is how it knows to turn on and will not work without it.

[Wolf Fabrication]

Truck is wired with an external voltage regulator. That VR simply gets power from a keyed ignition source, then it had one wire going to the Field terminal on the alt. I think the alternator charge wire goes to the starter solenoid where it meets the battery, or might run to the ammeter, I need to double check.

Whats the easiest way to make this work?

[Ren Ching]

Factory setup for a Series III using the same alternator would probably be the closest thing to the load requirements of your truck. I just double checked the diagram to be sure- it goes like this:

Heavy gauge #8 (factory used brown) or so probably sufficient for the loads your vehicle will impose on the alternator. Run this directly from the large spade furthest away from the small IND spade to the same large solenoid or switch post that the main battery cable goes to.

Run another wire smaller gauge say #12 or so (also brown if you care) from the other large spade to the same terminal on the solenoid.

Run a third wire (factory used brown with a yellow trace directly (actually there were a few connectors in there) to the charge light on the dash. There should be a white wire coming off the other side of the charge light going to the ignition-switched side of the fuse box. Make the brown/yellow wire the same or similar gauge as the white wire.

I'll email you the diagrams.



Truck is wired with an external voltage regulator. That VR simply gets power from a keyed ignition source, then it had one wire going to the Field terminal on the alt. I think the alternator charge wire goes to the starter solenoid where it meets the battery, or might run to the ammeter, I need to double check.

Whats the easiest way to make this work?

[o2batsea]

Having the correct battery light wiring is essential for the alternator to work. This is how it knows to turn on and will not work without it.
So, if the bulb in the charge light burns out you have no voltage sense current?

[Red90]

So, if the bulb in the charge light burns out you have no voltage sense current?

The wiring schematic shows that stock Defenders have a resistor in parallel with the light, so it will still function with a dead bulb. I've never looked at what is physically installed.

[Wolf Fabrication]

So, if the bulb in the charge light burns out you have no voltage sense current?

That was my question too.

So in theory, why not just run the IND to a switched power source?

[Ren Ching]

yes that is the case on the SIII's. As John says there is a resistor on the 90's to deal with that problem. Interesting, John, I did not know that until you pointed it out. Checked the diagram to see it myself. Though, have not had that issue with any of my Series vehicles.

FYI Jonathan, saw this in the 90 shop manual:

attery not being charged
AUTION: The vehicle
attery must never be
isconnected while the
mgine is running


So, if the bulb in the charge light burns out you have no voltage sense current?

[Wolf Fabrication]

FYI Jonathan, saw this in the 90 shop manual:

Battery not being charged
CAUTION: The vehicle
Battery must never be
Disconnected while the
Engine is running

Thanks Dave, my hand has been slapped enough.:)

[Red90]

That was my question too.

So in theory, why not just run the IND to a switched power source?

Because there is no limit on the current.... When you turn on the switch, with the alternator off, it will dead short through the IND terminal. The bulb or resistor provide a small load.

[Wolf Fabrication]

Interesting find on RN: http://www.roversnorth.com/store/t-technical-info-tips-alternator-conversion-wiring.aspx

In their conversion they show keeping the VR and simply reconnecting the Field wire to the IND terminal.:confused

[Red90]

Interesting find on RN: http://www.roversnorth.com/store/t-technical-info-tips-alternator-conversion-wiring.aspx

In their conversion they show keeping the VR and simply reconnecting the Field wire to the IND terminal.:confused

You need to read again... They are bypoassing the regulator. The dotted lines are jumpers you are supposed to add after disconnecting the regulator....

Remove F wire from voltage regulator and small charge light wire from D terminal and connect together for IND light circuit.

Remove the large D wire from the regulator and connect it to A and A1 wires from the regulator

I would run more than one 10 gauge wire for 65 Amps. Two 10 gauge or one 8 gauge would be barely OK.

[Wolf Fabrication]

Okay, I misunderstood. On my truck, I have one wire coming off the VR Field terminal and disappearing into the harness heading in to the firewall, then at some point another wire comes out and goes to the field terminal on the old alternator.

[Wolf Fabrication]

Thanks everyone for your help. Everything is wired up and appears to be charging correctly.