THIS is why you learn to continue your research and only add what you read from members to your research. Alternators are NOT that complicated themselves, so it is HIGHLY possible to goto a salvage yard, find a car that has obvious signs of OTHER problems (like body or interior), and get a decent alternator from it. No offense to anyone, but some folks believe in solving problems by throwing parts at it, NEW parts. In my vast experience with these and all my other cars, when youre not totally certain what the problem is, buying a used or salvage part , for 50, is worth the money saved if you find out the problem doesnt get fixed.

 

In the case of the alternator used on this vehicle (LR3/D3/RRS) the ECM controls the alternator output via a PWM signal per this excerpt from the maintenance manual:

"The generator comprises a stator, a rotor, a rectifier pack and a regulator. There is a three-pin connector (C0053) on the generator: Pin 1 – Voltage reference line to the battery via the Battery Junction Box (BJB) Pin 2 – Pulse Width Modulated (PWM) signal from the Engine Control Module (ECM) to the generator (generator control) Pin 3 – PWM signal from the generator to the ECM (generator monitoring) The generator is connected to earth via its mountings."

To properly test this alternator (generator) then, you need some means to look at the PWM signal going to and from the ECM while monitoring the battery voltage, which means a dual trace oscilloscope in conjunction with a multimeter would likely come in very handy. I haven't done this, but I do have a dual trace oscilloscope plus several analog and digital voltmeters.

Venturing a guess that if the battery voltage does not change then the ECM is not sensing or telling the regulator to increase/decrease charge rate, so that either is a wiring problem or perhaps a problem with the ECM. My personal experience with automotive electronics is that they are very robust, usually only failing as a result of human error or physical catastrophe, there are always exceptions though. Does anyone know if this ever was resolved satisfactorily or did the OP send it to Valhalla (drive it into the Pacific)?

 

i agree with everything said. i felt this was eith the main problem OR the problem killing the alternators. Ive went thru 3 and currently working on diagnosing my 4th alternator issue, on the same lr3 range rover sport hse. Alternators are usually NOT high fail objects. They dont last forever, but they are not Known for only lasting a few months at a time. Ive worked on Dodges where one pin of the two pin connector allowed the alternator to charge if you applied voltage to it. So im aware of the computer controlled alternators. This is why i DONT recommend just buying a NEW one at first. Ive had alternators that wouldnt charge on the landrover but passed MULTIPLE tests at autozone/o'rielys. super annoying. Right now mines is not charging again. I have a clamp meter, and i can see the battery putting out amps to run the car, but nothing coming from the alternator main cable. Ive disconnected the ecm connector, found pin 96 and found continuity at pin 2 on the alternator connector. Strange thing is, when the alternator is plugged into the alternator, that Pin 96 has continuity with pin 95,94,93, and GROUND. Anyways, im not gonna buy another alternator yet until Ive confirmed %1000 that thats the fault. The parts stores here dont give you money back if it doesnt work. and two days ago it just started charging for 1 out of 20 starts.

 

If your DC clamp on does not show anything going to the battery than obviously the alternator is not putting out. You will have to find some way to check that the alt_mon, alt_com and Batt sense leads all have signals on them. There is a Fuse 20E in the Junction Box (engine compartment) for the reference battery (Batt sense) lead and there is a 400 amp fuse at the battery, all connections should be checked thoroughly.The pin 96 to 95, 94, 93 and ground I have no idea of, that is internal to the ECM and we are not privy to the electronics in there...
I am assuming you have the V8 gasoline powered version?

 

These are some diagrams to this alternator ecm relation. The pin 96 was putting out 6.91v at idle. the battery voltage was 12.2. I kept the battery charger on the main battery. None of the other mentioned pins on the ECU relate to Ground at all during continuity checks, however, when the alternator pigtail is plugged in, all of the pins (96,95,94,93, ect...) connect to ground. Im tempted to disconnect the battery, disconnect the pigtail at the alternator, bridge the pins together to see which one relates to all the mentioned pins. Then it would make sense that the alternator may have a short to ground (its casing), and by connecting the pigtail bridges the shorted pin with one of the other two , causing the 5+ pins on the ECM to meet GROUND, all while NOT giving errors from the PCM. One of these pins being Fuelpump control. Otherwise, theres either a short in one of the many othe devices connected to these pins, or the ECM is going bad. On a side note, If it is the ECM, should i be able to manipulate the alternator somehow just to confirm it charges? It must be possible seeing as Autoparts stores can get these alternators to pass flawlessly, and they test several functions of the alternator. Besides, this is a 2006, should not be able to defeat our 2020 minds lol

 

I have not tried it on my LR3, but you can generally use any alternator on any vehicle as long as you can get the belt/pulley and regulator to work properly with each other. This Pulse Width Modulated Alternators article gives you some general knowledge about how these PWM controlled alternators work, you'd need a drawing of the internals of the alternator to generally understand how autoparts stores can test them. I'm going to read up on them a bit more, this thread is making me curious...

 

That's not the way to test an alternator. To properly test the alternator you need to do it at the alternator and also do an AC check for a bad diode pack. Do the test properly before deciding your alternator is kaput. Testing across the battery as described is a good place to start, but it's not a proper test of the alternators condition. Denso are the ideal replacement.

 

Well this is quite interesting so I ordered an alternator to conduct some testing, plus a read of the Ford portion of this article https://gearsmagazine.com/magazine/h...rging-systems/ reveals that the PWM signal is used to control the field current, thus increasing or decreasing the ampere output of the alternator (who'd a thunk it?). The higher the duty cycle of the PWM (128 Hertz?) signal is, increasingly more output from the alternator, so although more complex electronically, it helps with efficiency. Am learning lots about modern alternators...

 

Very interesting - keep going

 

Yes, This is like on the (modern) Dodges, where im able to make the alternator do its job by applying power to one of the pins on the 2pin connector. I think this has to be in relation to these non charging issues. Maybe not directly, but indirectly. Either that or these "original Denso" alternators are just THAT bad quality. This is also why im hesitant to just buy a brand new one. Im too stubborn and logical. It doesnt make sense that you can take an alternator from a working vehicle, succesfully test it at auto parts stores, install it on your vehicle and when it doesnt charge, its the alternators fault. Its a shame bcuz other than that, these Post- BMW Range Rovers are really reliable.