Series III Alternator charging issue

[vee12eman]

Hi all,

A question for the electrically minded amongst you all. The car, a 1971 Series III 2+2 with standard electrical, was out for a drive today on a dry, warm day. No previous symptoms. The round trip of around 100km, was completed without incident and, at the turnaround point, the car was started and stopped a number of times; again no problem.
On the way out I noticed the charge light was illuminated. Changing revs made no difference and the performance of the car was unaffected. Like an idiot, I made no note of the voltmeter reading. As I said, I stopped at the destination, started and stopped the car several times to move it ? no problem.

The car made the return journey, mostly freeway/motorway with no further incident, although the light remained as before. On stopping and with access to tools, I measured the voltage at the battery with a multimeter; 12.2V with the engine running. With engine off, the reading rose to 12.3V. The car starts and stops fine and finally I thought to check the voltmeter on the dash, confirming the multimeter reading; the gauge just rose out of the red, but below 13V.

I adjusted the voltage output adjustment of the separate BUTEC regulator, to both the high and low end of the scale ? no discernible difference.

The Alternator was reconditioned by a reputable company and sat for some time before use, but worked well till now. The wiring loom is new and the whole system has only done around 2000 miles owing to other commitments, the car is garaged in the dry and has seen little rain since completion, none recently. The BUTEC regulator is the original with no modification/work except cleaning.

Being the rather unusual BUTEC/Leece Neville alternator, there are several differences to the Lucas types and I am not all that good with alternators generally.

Does anyone know what these symptoms are likely to indicate, how to carry out further tests if necessary to isolate the problem and of course what I can do about it?

All ideas & suggestions welcome!

Regards,

Simon

[MarekH]

Dear Simon,

The charge light is on when there is a voltage difference across it. One side sits at battery voltage via the white wire and the other side is at alternator voltage via the brown/black wire. Once the alternator starts feeding the battery, there is no difference, so the light goes out.

It sounds as though your alternator is not putting out any voltage and you are running on battery power. Follow the same trouble shooting tips as for any other alternator/regulator. The usual cause is that a diode has failed as the regulator is pretty bullet proof.

All of the parts are easily rebuildable as they also were used in trucks/ambulances and fire engines during that time period. It's a shame you've moved to Oz:- I have spares in the attic.

kind regards
Marek

[tinworm]

Just agreeing with Marek . Your battery will go a long way without current from the alternator which I think is what you are witnessing. The dip in voltage when the engine is at rest and the ignition turned on is due to the small loads being borne by the battery - every load will decrease the battery voltage further - the heavier the load the more the decrease. The alternator voltage must overcome (ie be higher than)the battery open circuit voltage to allow charging of the battery. If you have tested the battery open circuit voltage (no loads connected) and this reads 12.5 v a functioning alternator will show around 13v at the battery terminals with the engine running.A quick test for this without a multimeter would be to turn the headlights on without the engine running with the front of the car pointing into a dark garage and note mentally the brightness of the lights - then start the engine - the lights should get brighter as the engine is revved above 1500 rpm - if they dont no charge. First thing I would check would be the slip ring brushes , if these are worn they dont make contact with the rings they can also stick in their holders and (believe it or not) you can sometimes jar them back to contact by giving the alternator a smack with a block of wood (!)

regards Barrie

[vee12eman]

Thanks for the responses,

I did suspect there was a problem with the alternator itself, but obviously the regulator could also be a factor. As one of my main aims with this car is to learn and do the work myself, can anyone point me at a site (or whatever) which will explain how to test the items? I much prefer to do this myself and repair the alternator or regulator myself if possible.

I will have a look to see if the brushes are sticking/worn too, I'll see if I can find a suitable lump of wood (and proceed carefully!).

I assume that if I connect a voltmeter across the alternator from the large brown wire connection to earth, that I can measure if the alternator is giving an output? If so, then again I would assume the alternator is OK and the regulator at fault. I guess I have to have the thick brown cable disconnected at this stage to prove output is from the battery, will this cause any damage to car or alternator?

Again, all input appreciated.

Regards,

Simon

[AussieEtype]

In the late 80s I had similar problems but I could not diagnose the issue - I went to Dick Smiths and bought the diodes that go in the alternator and replaced them but still had a problem.

I pulled the the regulator out and took the cover off and the circuit board was corroded - I made a new circuit board from bits purchased from Dick Smiths and took the components off the old board and soldered them to the new one and replaced a few of the commonly available components from Dick Smith.

Fixed the issue and 25 years later still working fine so was the regulator - Dick Smith no longer sell electronic components but Jaycar do and some online businesses.

Good luck with it.

Garry

[tinworm]

Hi Simon , an alternator will not work without a dc supply (from a battery) to excite the field coil. The regulator varies this dc supply (in this case 12v) from 0v to 12v using circuit voltage as a reference so if the regulator senses the circuit voltage is above 13.5v it will reduce the excitation by dropping the voltage it supplies to the field coil (through the slip rings) nearer to 0v . If it senses the circuit voltage is less than about 12.5v it will increase excitation voltage of the field coil towards 12v. it performs this juggling act instantaneously and will supply more excitation if you turn the lights on or something to draw more current from the battery. Ordinarily you need to see if the field coil is getting a supply. I cannot be specific to your car I'm afraid as I am not lucky enough to own a series 3.

hope this will be of use Barrie Wood

[vee12eman]

Hi guys,

An update on this issue for those interested.

The new, rebuilt alternator bought at Stoneleigh in about 2005, but not fitted and used until the car was finished around 5 years later, was at fault. I managed to source a new one from eBay USA which cured the problem This was expensive, but I didn?t have to provide an exchange item so I can now fix mine as a spare for the future.

I have ordered a new regulator as well, but this has not arrived yet. The fitting of the new alternator allowed me to test out the original regulator as described using info you guys kindly helped me to find and understand.

I realise now that there is actually good information in the Series 3 Workshop manual (Original Jaguar publication) which tells you how to dismantle and test the alternator. For some reason I did not think the manual would go to this depth, hence I did not look?duh!

Anyway I have tested the field diode pack which is definitely not working, but this can apparently be symptomatic of other faults ? normally in the rectifier/heat sink assemblies. I will be dismantling and checking further later on. In the meantime, does anyone know a source of new field diode assemblies and heat sink/rectifier assemblies, or can I actually change the diodes in the heat sink assemblies, if so, what value do they have?

Thanks again,

Regards,

Simon

[71 V12]

Hi Simon,

The diodes are replaceable. It is some time since I did the job, but as I recall the diodes are push fit in the heat sinks. I recall using small splice clips to attach the lead on the new diode to the existing wiring, covered with a heat shrink tube to insulate.

I found the diodes on line after some research to identify the type, sorry I just cannot remember what they are or where I got them. I will check to see if I retained the receipt.

Worth having a go.

[vee12eman]

Thanks for that, I will be having a go soon.

Sutton Coldfield eh! Know it well as I was brought up in Great Barr, that brings back memories!

Regards and Thanks,

Simon

[71 V12]

Hi Simon,

It was my daily walk to school in Sutton Coldfield, passing on my way a heather V12 coupe frequently being reversed out of a driveway on Wylde Green Road as I passed that sparked the passion for the V12 E Type.

Jaguar also sourced a significant amount of the E Type in the locality, carbs and driveshafts in Erdington, axles in Witton, suspension in West Brom. A very significant association with Jaguar going back to the birth of the company, and as strong today as ever. But I guess this is true right across the West Midlands.

Back to the diodes, I got them from this company http://www.jcrsupplies.co.uk. I can't find a reference to the actual part number for the diodes but I think there maybe a reference on the original diodes that will be visible when you get the heat sinks out. I think they are a standard type easily obtainable.

Good luck and update the thread when you find the source, I think there could be a lot of interest. I am annoyed with myself that I did not keep the diode details.

Kind regards,

Kevin

[vee12eman]

Hi again,
Well I was going to post to say I had fixed the problem, but it?s back. I bought a new alternator and fitted it, the problem went away. Then the new voltage regulator I had ordered arrived, so I fitted that ? the idea was to get the original alternator fixed then hold both as spares. Unfortunately the new regulator didn?t work with the new alternator ? same issue as before, charging light on and a low voltage at the battery and on the voltmeter. Put the old regulator on and the problem goes away. The regulator was sent back but no report on its? condition, replacement or refund as yet. Anyway, car does a few more Km ? around a hundred, then the charge light starts to come on again, firstly with slightly reduced voltage output and goes away at higher revs, then comes on at higher revs and finally on all the time. All this was within a distance of around 30 Km. I tested the wiring, it looks OK.
Has anyone, PLEASE got any ideas what could cause this. The alternator was expensive and now I don?t trust the design, is there a better modern alternative? Remember the alternator of a Series 3 points forward and rotates backward ? not a problem for an alternator, but it is for the fan which cools it.
Incidentally, I tested the original alternator, windings and stator seem fine, the field diode pack is toast and the internal diode/heat sinks test seems to reveal they are not working, but I suspect my test equipment may not be ideal for the task, so I would not be certain of the results at the moment. The field diode pack of the new alternator tests OK, but I haven?t dismantled the unit to check the internal components.
Regards,
Simon