Alternator - Not charging

[walc100]

Looking for some idea's here,

Been searching away but haven't nailed it yet

Wife's RRS intermitant not starting over the week, battery so ordered one before getting home. Had my father swap it over and he has relayed voltage only getting to 12.6v idle.

Since then she had been stuck again.

Where do I start when i get home?

Alternator?

Or power leak?

Matthew

[Barryp]

Sounds like failed alternator.
Voltage should be up around 14V at a bit above idle, can't remember how low it gets at idle but it is above 13V.
Regards
Barryp

[walc100]

Seems like i have a dead short somewhere battery dumpt down to 2 volts in 3 hrs and very hot.

Alternator

[Graeme]

The alternators are known to cause a dead short when they fail.

[Graeme]

Whilst looking for other info in the WSM I read that the D3 alternator uses 6 Zener diodes. This prompted me to do some research as to why zeners are used as I had only encountered normal diodes in the alternators of older vehicles.

The original alternator inbuilt method to protect vehicle electronics from the high voltage load dump voltage spike (80-100V) that occurs when a battery is disconnected (or breaks internally) while the engine is running is to replace the 6 standard power diodes with power zener diodes which allow reverse current flow once their trigger voltage is reached. The theory is that this creates a temporary almost dead short for the battery and causes the alternator to stop charging, with the current soon unable to travel in the reverse direction due to the low charging voltage no longer exceeding the zener trigger voltage.

A newer, better way is to retain the 6 standard power diodes and add 3 power zener diodes to return the excessive voltage to the alternator's windings once their trigger voltage is reached. This method is better because the zener diodes in this design don't normally conduct so their temperature is always at the casing temperature and therefore neither the diodes nor their solder joints deteriorate, compared with the 6 power zener design where the diodes get hot from their inherent voltage drop during constant use and therefore will eventually fail. Normal power diodes normally go open circuit when they fail, zeners can go either open or short circuit with the short circuit instances far too common.

Unless I can discover that my D4's alternator does not use the same load dump protection method of 6 zeners, I intend moving the alternator's B+ cable connection from the starter motor directly to the battery but via a 200A mega-fuse so that when the diodes or their solder joints fail the fuse will blow and leave the battery intact and the vehicle driveable, to some extent at least.

[bbyer]

I have a petrol 4.4L V8 LR3 and just noticed after reading your post that yes, the thick cable off the alternator runs first to the starter motor and then up to the battery.

That struck me as odd. Is it that this arrangement is uncommon or is it just that I have not paid too much attention to battery wiring schemes?

My experience here is North America with GM pickups and the like, (V8 rear wheel drive), is that the alternator cable, (a not so thick one I might add), runs directly to the positive post of the battery, with a fusible link or similar, and that additionally a thick cable runs from the positive post of the battery down to the starter solenoid.

I can only assume LR was trying to save on wiring or something? With GM, the alternator is generally mounted on top so the battery may not be very far away whereas if the alternator was underneath the engine, well then cable lengths would be longer. If that is the only reason, your idea of a separate fused cable is not radical and has alot of merit; so much that perhaps LR should look at going back to the old design.

The wiring design they have just appears to add more challenges as I see it and with not much of an upside. A starter motor or starter solenoid with an internal short could suck power directly from the alternator such that the full alternator output never gets to the battery.

It also makes it hard to measure alternator output with one of those sort of wrap around the cable amp meters. This sounds so Land Rover!

You just may have come up with a very practical mod here.

[Graeme]

I expect the cable to the starter is only saving the cost and weight of more cable length, 1 less fuse and 1 less cable to connect, but perhaps a little less voltage drop too. The wiring diagram shows 35 mm2 cable (just over 2 B&S) from the alternator to the starter then 50 mm2 cable to the battery via a 400A mega-fuse. I'll follow the starter cable with a protected 2 B&S cable directly to the alternator with the 200A fuse at the battery.

If in time the alternator dies due to failed power diodes I'll look at replacing them with normal power diodes if suitable ones can be found and add suitable zeners running off the regulator supply diodes back to each field winding to shut down the regulator rather than shut down the high-current output.

Reference: AN1969 datasheet and application note, data sheet, circuit, pdf, cross reference | Datasheet Archive (http://www.datasheetarchive.com/AN1969-datasheet.html)

Edit: May try a 175A fuse first.

[bbyer]

I regard the idea of running a separate cable off the alternator directly to the battery as having a lot of merit. You are looking at the mod from a view of alternator problems and for me, starter motor problems. Land Rovers view is that when all is working perfectly, it does not matter and I guess they are also correct when all is working perfectly -dah.

Regardless, your mod tends to benefit both concerns. As such I got to wondering how to actually do the mod.

It appears to me the simplest would be just to disconnect the starter to alternator cable at the alternator end and tape it up. Then run the new cable from the alternator up to near the battery and mount the MEGA fuse and then from there a second short cable to the battery.

I then got to looking in the battery fuse box and wondered if there was any way of mounting the mega fuse in there and then just hooking to the existing fuse box to battery cable already installed and if so, was there a downside.

One might even get away with a 150 amp MEGA fuse as the Littelfuse appears to have some sort of slow blow feature; per the attachment below and compatibility, 150 amp is used somewhere on the Freelander, not that 25 or even 50 amps means much in a short circuit situation so 175 is probably better.

Littelfuse MEG150 - MEGA Fuse | O'Reilly Auto Parts (http://www.oreillyauto.com/site/c/detail/LIT0/MEG150.oap?pt=N1175&ppt=C0172)

[Graeme]

Mounted and inline fuse holders are available. IIRC my alternator is 180A so a 175A slow blow fuse may be sufficient but perhaps not when a winch is in use especially, if the engine revs are above idle.

Edit: I might just fit an inline fuse to the existing cable near the starter motor if it can be adequately supported.

[LowRanger]

There is quite a lot of info here http://www.aulro.com/afvb/d3-d4-rrs/133707-alternator-failure-without-warning-can-anything-else.html.

[bbyer]

Edit: I might just fit an inline fuse to the existing cable near the starter motor if it can be adequately supported. If the location of the starter motor in the diesel is anything like the location for the petrol V8, one could say that there is a lot of support for anything you can get in there.

There is so much stuff surrounding the starter motor such that it is near impossible to get the starter motor out - well just a minor miracle and a very patient mechanic with small hands, plus the ability to feel whatever if he lacks X Ray vision.

This compares with getting at the alternator which is comparatively easy - it only takes above average mechanical skills and a couple of hours I would say. That is why I figured that disconnecting the starter to alternator cable at the alternator,taping the end, and installing a new alternator feed up to the battery was the most practical, and yes, an inline fuse located somewhere near the battery end would work probably the best as one could then get at the fuse to inspect it.

I have a feeling that we are stuck with the zener diode alternator design as I suppose LR is not the only one Denso makes this alternator design for. As such, short circuit proofing the alternator feed for the 3 and 4 is probably the best we can do.

[Graeme]

The starter to alternator cable on the 3.0 is very accessible so shouldn't be much of a hassle fitting an inline fuse.

I'll be asking my SIL this w/e how his employer's alternators accomplish load dump protection. He doesn't have a high opinion of the brand that LR uses but perhaps that's understandable.

Edit: Whilst the cable is accessible the ends are not as the starter probably needs to be unbolted to access the power terminal and the alternator is well hidden.

[Graeme]

There is quite a lot of info here http://www.aulro.com/afvb/d3-d4-rrs/133707-alternator-failure-without-warning-can-anything-else.html.
No-one got to the bottom of why the diodes fail short circuit, but now knowing that they are zener diodes and are meant to conduct in the reverse direction once their trigger voltage is reached, it becomes clear that if a power diode fails or if the regulator fails high so that excessive voltage is produced, a short circuit of the battery will occur. However as zener diodes only conduct in the reverse direction whilst their trigger voltage is exceeded yet the current draw becomes permanent, it seems that the zeners themselves must be failing. Using zener power diodes will always expose the alternator to creating a dead short for the battery, whereas using standard power diodes and then zener diodes to shut-down the regulator supply voltage does not expose the battery to the possibility of a dead short.

As suggested in the above thread, a fuse in the alternator B+ cable would prevent the battery from being drained. A better-designed (more expensive?) alternator might not be so prone to failure. If LR had anticipated alternators failing with shorting zener diodes they might have run a seperate, fused cable. However I doubt that LR's alternator specifications to prospective manufacturers include modes of failure.

[Tinman]

Had the same charging problem on my 2005 D3 just recently the alternator light even came on for a few seconds then went out. After checking the charging it was around 13.4v quite a bit low. I removed the alternator fuse and re inserted it then started it again. The battery was then charging at 14.4v so I thought everything was OK. A few days later took car up for rego check, left it their, received a phone call about 2 hours later explaining the car had a melt down. Apparently after they moved it to do the brake test smoke came from under the bonnet, you guessed it the alternator packed it in. So a new one was installed. Just reading about the zenner diodes this may have been the problem as at one time away just recently the main battery went dead overnight for no reason. Or maybe the alternator got to the end of its life any way $900 less in my pocket now but car is going great

[bbyer]

Early this spring, I ended up replacing my factory alternator with a rebuilt.
I had an independent install a Wilson (WAI) as that was all that was locally available on short notice other than dealer supplied which was about double the money. I could not believe that a LR supplied Denso rebuilt would be twice as good as a Wilson. In reality it may be true as the independent had to install a second a week later due I think to "regulator" failure. Actually they did it a third time as the second unit shipped with a 6 groove pulley and the petrol V8 uses 7 grooves. To date, the independent has not changed his outside sign to add the Land Rover logo advertising vehicles he is comfortable with.

I kept the core with the idea of tearing it down to find out was was wrong with the factory unit. In reality I did not succeed as most of the little screws would not unscrew but instead the Phillips heads tended to be destroyed. I was hence stopped and have not proceeded as what I did realize that if I got it opened up, it was not clear I would be able to get parts as needed. At the same time, perhaps I would then know what was wrong however so the idea still lives. Part of me thinks it is the regulator and that is difficult to test with old style techniques - well impossible.

What I have noted is that while many talk of self rebuilding the alternator, it is not clear to me that anyone really has, (well maybe a half dozen or so), as no once can seem to find parts - certainly not me and if they do, no one seems to provide part numbers or sources.

That is me anyhow and I do not know anyone in the trade that will actually help out so to speak. It just seems that the craft practises of old still prevail when it comes to alternator rebuilds, or almost no one knows.

I cannot believe that Denso has built an alternator that is unique to Land Rover and no other vehicle manufacturer installs a similar design. I can however believe that the PWM "regulator" part is unique to Land Rover. I also expect that the regulator in the D3 is different from the regulator in the D4 alternator, hence one cannot even substitute alternators even if they mechanically fit.

If the regulators were identical or interchangeable, I expect that installation of the slightly larger 180 amp alternator of the D4 would solve a lot of the D3 alternator problems - but not the D4 problems. This presumes that the D4 alternator rating is not badge engineered and that something inside is "bigger" than with the D3. Ideally it would be the diodes, (zener or otherwise), and that they would both mechanically and electrically fit within the D3 alternator frame - but now I am back to the parts problem.

[Tinman]

My wife has just come back from Port Macquarie NSW where she took our D3 with a engine fault code that came up on her trip anyway when I spoke to the service guy there he told me that they have had to replace quite a few alternators, so it seems to me that there must be a problem with these alternators. I know they have to pump out quite a bit to keep these guys going but to fail in such a short time keeps me wondering. As far as repairing alternators I repaired one years ago but in this day and age everything is throw away so I sometimes just go with the flow

[bbyer]

As far as repairing alternators I repaired one years ago but in this day and age everything is throw away so I sometimes just go with the flow I suppose at least in the case of the alternators, they do get repaired, but rather than locally, at some distant location.

As best I can determine, parts are not available for our alternators as the test equipment required to determine fault is too specialized to invest in. As such, only some centrally located facility that can accept volume can afford the equipment required.

Then there is the question of parts. I really think the regulator is unique to our vehicles, hence a combination of the cost of stocking a low volume part plus the fact that one needs a special tester even to determine if it is defective means local repair is just not economically practical. Since local repair or testing is not really possible, then it is difficult to even figure out what is failing on our alternators or what is the part that fails most often, (probably the zener diodes).

Still, I would like to know what goes wrong. Maybe the alternator just another of those time use parts where after so long in service, (3 years?), one should just be replacing it - kind of like it was a brake hose.

[Old Farang]

Very interesting discussion, and information on this thread.

I am getting a bit long in the tooth now, and not up with the latest technology, 3rd brush generators and the odd carbon pile rectifier were still in use when I started off!

However, I spent a big part of my working life in the electrical industry maintaining large, variable speed, DC drives, both with old “Ward Lennard” type systems, magnetic amplifiers / saturable reactors, and more modern SCR systems of various types. I am referring to 1,500—2,000 amp drives, and 800 hp motors.

The only basic difference with an SCR system as compared to an automotive alternator (apart from the voltage), is that with the SCR system the bridge rectifiers are gated and conduction is controlled to give a variable voltage output, rather than continuos conduction, or commutation, for a fixed voltage with an alternator. In both systems the source is a 3 phase AC voltage.

In my experience the two most common faults encountered with failures of the actual diodes were caused by: excessive heat / lack of sufficient cooling; and / or a diode with a low PIV( peak inverse voltage) rating used in a system that was prone to producing unwanted spikes, or “glitches”, as the Americans called them.

The alternator in my old D1 gets that hot I try not to think about when it is going to melt down! But it seems happy enough, and as the car does not have a great amount of electronic systems in it, voltage spikes do not appear to be a problem.

I am not sure where the term “load dump” is coming from? To produce a spike on an automotive system sufficient to damage the power rectifiers of the alternator, I would have thought that it would have to be generated from the switching of an inductive type of load, such as an electric motor somewhere on the system, which maybe what they mean. In the link article they refer to disconnecting the battery as being the cause of “load dump”. I am not aware of anybody likely to be doing this while the alternator is running, and if they do then they only have themselves to blame for any subsequent failure!

The explanation of how the alternator generates a voltage, while basically correct, can lead to some misconception of the actual process. They are again blaming the battery, which is not the cause at all. Automotive alternators use what is termed “machine sensing”(mostly), as compared to battery sensing, to control their output. The internal voltage regulator usually consists of a voltage divider network and a reference Zener diode, which controls the excitation to the DC rotor windings, which in turn determines the output voltage of the alternator, usually around 14.5 volts dc.

Directly after starting the engine the battery voltage will have dropped from cranking the starter and any energy used maintaining whatever systems the vehicle has active while not actually running. The alternator will respond to this lower voltage by charging the battery, as expected. But it does not suddenly get the battery voltage up to the desired level and then abruptly stop charging, thereby causing a “load dump”. The charging rate will taper off in a smooth manner as the voltage of the battery increases and opposes the alternator output voltage, which can be considered a fixed voltage. Once the two voltages are equal no further current goes into the battery, unless there is a big demand on the system, such as a winch, which causes the battery to supply energy beyond what the alternator can provide, and its terminal voltage drops again, so repeating the cycle of charging and maintaining the battery voltage. At no time will this process cause any condition that could be referred to as a “load dump”.

As mentioned above, a “load dump” is more likely to be seen on the system when some, probably inductive, load is switched off causing a voltage “spike” to appear on the system, the magnitude of which may exceed the PIV rating of the diodes in the rectifier bridge, causing failure.

I was surprised to read of the use of Zener diodes in the power rectifier, although there are several different types of Zeners with different characteristics. I can see why they have been used in an attempt to overcome the problem. But their use may be part of the problem, as in using the alternator windings to “absorb” the energy of any “load dump” they appear to have overlooked the complete picture, as it is possible that the alternator stator windings are, by transformer effect, inducing an over voltage into the field windings, which in turn, is destroying the voltage regulator connected across it.

They point out in the link article that the “load dump” voltage can be in the order of 80-100 volts, for a duration of 300-400ms. But again, they are assuming a complete disconnection of the load, which does not happen---even if you disconnect the battery while the engine / alternator is running, there is still a measurable load on the alternator.

Also in the article they correctly state that there are two ways to try and prevent damage to the alternator: either within the alternator, or externally at the point where the problem originates. In my experience it is the latter method that has been the more successful. These “spikes” are transient, and as such are very difficult to both measure and either control or suppress, especially in an automotive system where all the various loads are in effect connected in parallel. If it can be tracked down to just which sub system or accessory is causing the problem, then it is possible to address it directly at the source.

I would also point out that it does not matter one iota where the output wire of the alternator is connected: at the starter solenoid or directly at the battery + terminal, it is just either end of the same cable that connects both the starter and battery.

From some of the postings it appears that when the alternator has failed it has very rapidly flattened the battery, and it is suggested that a mega fuse of around 200 amps may help prevent this. While this modification will not do any harm I have to question just how much current has been involved in those cases where the battery has been run flat. I would suggest that it must have been a lot less than 200 amps, because even that level of amps would have very soon led to a melt down of the wiring at the best, and more than likely a fire. A better method may be to route the alternator output wire via a suitable relay—just like the old “cut out” relays used in days gone by!

Sorry to ramble on so long, I just hope some of it is helpful. I would be interested to learn just what purpose the latest alternators having a connection to the vehicle ECU are trying to achieve. (if that is what I understand from a posting?)

[Graeme]

The load dump referred to is that caused by the disconnection of the battery either accidentally, purposefully or by the battery going open circuit due a broken connection between cells whilst the alternator is producing significant charge. I suspect it is a rare occurrance but my understanding is that it is a standard that automotive systems have to achieve for some particular (EU?) certification. One has to assume that the zeners do their job when new but heat dissipation may be inadequate for longevity.

The suggested fuse will only be of use if the short circuit is severe but the fuse needs to handle the maximum alternator output. A dead alternator could be tested to determine what current that particular failure is capable of drawing to see if it is anywhere near the alternator's rated output, at least for the 1st few seconds before the resistance increases due to excessive heat.

I became aware of the certification of electronic equipment to withstand such load dumps when asked if my Llams module has been certified, as it is a requirement for vehicles used in Germany. I suggested that I would replace the module FOC if destroyed by such an event. I suspect vehicle manufacturers have adopted the approach to endeavour to contain the effects of such a load dump within the alternator rather than within every electronic module.

Edit: ECM control of the alternator is for reduced idling emissions and for reduced fuel consumption whilst accelerating (preferably only whilst coasting or decelerating) by preventing high charging unless absolutely necessary.

[bbyer]

I would also point out that it does not matter one iota where the output wire of the alternator is connected: at the starter solenoid or directly at the battery + terminal, it is just either end of the same cable that connects both the starter and battery.

I would be interested to learn just what purpose the latest alternators having a connection to the vehicle ECU are trying to achieve. (if that is what I understand from a posting?) I enjoyed your post. You are correct above when you say that it does not matter where the alternator output wire is connected. I would say that is particularily true when all is working as intended.

My reason for wanting alternator output to got directly and separately to the battery has to do with with was a common trouble shooting technique over here, at least in the past - being able to insert a clamp meter over the alternator line independent of the starter motor cable or where provided, the third wire that goes to the vehicle fuse box to power all else. It was nice to be able to separately measure the amps output from the alternator and the amps going to the fuse box and knowing that the starter motor was on its own wire as well. The difference in the numbers would kind of tell you about how much was going in or out of the battery.

Re the Pulse Width Modulated (PWM) internal regulators now taking their orders from the EMU, Engine Management Unit, rather than what I would call the the regulator sensing the electrical system, (what you called Machine Sensing), these new style regulators delegate their command function to the EMU and do as they are told.

As Graham said, the EMU may decide based on Emission concerns that it will load shed rather than tell the alternator to increase output. In the case of the 3, this can meaning cycling the heated seats, windscreen, radio amp etc rather than increasing engine rpm. That is how I understand it anyway.

[Old Farang]

Thank you very much bbyer for posting those links. Very interesting and informative!
I not only need a walking stick to get around, looks like I may need one to keep up with modern developments! :(

However, I still stick to my original post concerning the "load dump". I very much doubt that that the reasons Graeme has posted concerning the battery are likely to occur and be the cause of damage. Transient spikes on the system are much more likely to be generated from the switching of loads other than the battery, and such switching on and off is a normal part of the vehicles operation.

I just have to wonder where some of this modern technology leads to. In another post there were some comments comparing house wiring electricians to automotive electricians. The processes involved with some of this equipment is far from the domain and training of any "electrician", automotive or otherwise. The most common affect of this is the "throwaway" response to equipment failures, and its associated costs. cheers.

[Graeme]

I've been informed that the 2.7 TDV6 in the Ford Territory uses a LR spec alternator due to Ford wanting to keep development costs as low as possible so didn't consider specifying a different alternator. Whether its the 2.7 alternator or the 3.0 alternator is yet to be ascertained, but regardless the alternator B+ cable has a mega-fuse fitted to it. The alternator's rated output and the mega-fuse rating will be ascertained in a few weeks, although I suspect the information could be found on the net or from a Ford dealer.

I've also had confirmed that vehicle manufacturers don't tell alternator manufacturers how to build alternators (although some try), only what specification and tests the alternators have to pass including load dump testing. An example was a specification for load dump testing that required the alternator to be spinning at 18,000 rpm (approx 6,000 engine rpm), specific battery temperature preparation in a laboratory (presumably attempting to simulate an engine environment) etc then the battery disconnected for 10 seconds at a time for a set number of instances.

[bbyer]

Tested at 6,000 engine rpm and all I would like is for the alternator to last in a real engine compartment - asking too much I guess.

Finding a similar alternator in a Ford vehicle at I presume Ford pricing is real progress. I expect however that the PWM regulator will somehow speak a different language and we will be beat again or the plug shape and pin out, different. This is easy to do as the plug bits are effectively regulator plastic rather than alternator metal. I can only presume this is all done to protect us.

The mega-fuse numbers should be applicable however.

Now that I think of it, pulling the battery out while the engine is running is not exactly unheard of. In this country when it is cold and you are in the bush and you know you have a starting problem but you do not know what it is, yes, you will swap out batteries while the engine, heater, headlights etc are all operational.

The headlights are so to reflect back some light into the engine compartment so you can see what you are doing as it is noon and still dark; the heater, well the -40C feels a bit colder than usual as the engine fan is operational but it is cold air not hot that is blowing at you - giving a wind chill of maybe -60C. Usually in those circumstances we do not worry much about load dumping and voltage spikes - the bears and getting back to the bar are a bigger concern.

[ScottAU]

I have a petrol 4.4L V8 LR3 and just noticed after reading your post that yes, the thick cable off the alternator runs first to the starter motor and then up to the battery.


Sorry for digging up this old thread. I’ve got a 4.4 v8 petrol and this isn’t the case in mine, nor is it shown on the wiring diagram.

I'm chasing an alternator issue in my car at the moment, and I’m wondering if there is other significant differences between the V8 engines that might be useful to know. 156721