Non charging s3 alternator

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teegee777
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Non charging s3 alternator

#1

Postby teegee777 » Thu Jun 15, 2017 9:33 am

I'm helping a friend get his s3 v12 back on the road. We have an ignition light on, I've done the test of removing the regulator plug and shorting the field and negative, with no result. Can anyone confirm the alternator connections colours. We have brown/green in the blue and brown/red on the red. They are both Butec devices. Thanks
Image
Tony :England:
(providing support for a friends 1972 series 3 V12 2+2)

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SRK
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Re: Non charging s3 alternator

#2

Postby SRK » Thu Jun 15, 2017 10:55 pm

Turns out I had a dead alternator early this year and wound up buying a rebuilt one off ebay. To confirm I got the wires right I traded notes with the rebuilder and he sent me this:

"The important thing on the field input is the blue block and the red block on the brush holder. The blue block is negative input, the red block is positive. Also note that the black wire from the white rectangular triode located above the red brush holder goes to the positive field input, red block."

According to the wiring schematic I have Positive is NR (brown-red) and Negative is NG (brown-green) so I believe you have it correct in the picture.

Hope others can confirm. I'm traveling so can't go and check my car.

Steve

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vee12eman
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Re: Non charging s3 alternator

#3

Postby vee12eman » Fri Jun 16, 2017 12:09 am

Hi,

Firstly, what’s your name, much nicer to reply to a person – we generally suggest you make a signature block with your name in it – just your first name if you don’t want more detail showing.

Anyway, from the photo, all connections look OK. Some questions; is the alternator the one that came with the car and has it ever been working since your ownership? Have you replaced it and if so, where did you get the replacement? One issue is that some of the rebuilt units have the chassis isolated from the negative terminal, so you have to either remove the insulation (requiring the alternator to be stripped) or provide an alternative earth route to connect the terminal to actual earth.

With the Butec/Leece Neville/Prestolite alternator, faults can occur in the triple diode (triode); the white block at the top of your photo, the internal diode blocks (sometimes called plates, available in positive and negative), the static windings or the coil windings. The triode can be a little difficult to source (although is currently listed on eBay at £9.20,) but easy to replace, the internal diode blocks can be repaired by drilling out the old diodes and replacing with new (in fact I just found the same eBay company also advertises complete diode plates) and the windings/coil are generally not replaceable but tend to be pretty robust. Obviously, brushes and bearings can also be replaced if worn. Replacement units are very expensive, even as exchange units, but parts are actually quite cheap.

Regulator faults occur simply due to age of components and internal corrosion – much of the circuit board is exposed and original units are now over 40 years old. Another issue is the often overlooked earthing of the regulator to ground, however, you say that you have an ignition light, so this seems less likely. New regulators are available, based on a Leece Neville unit, from memory, this is the L5078R unit, but I recommend buying from a Jag specialist as they will have modified the terminals to suit the E-type wiring and you will get a warranty.

If you pm me with your contact details, I can send you a copy of an article written for the E-type club (sorry, can't remember which issue), which details fault diagnosis of the alternator and regulator. Used in conjunction with a fault diagnosis section in the original Jaguar Manual (available in the knowledge base), you should be able to determine if the Alternator is OK, alternatively it may be the regulator.

Regards,
Simon S-Y
Series III FHC

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teegee777
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Re: Non charging s3 alternator

#4

Postby teegee777 » Fri Jun 16, 2017 8:31 am

Thank you for the quick replies. So it seems we are wired up correctly and I get 12v in the correct places and the temporary short between the regulator plug connectors does not bring Alternator to life. The car has been off the road for between 10 and 15 years, and after many new parts and hard work is now ready for the road. The alternator was taken off the car about 3 months ago and supposedly checked out by a company, which is why we're surprised that it isn't working. I was a little concerned that the large brown feed wire has a slight indent where it met the diodes but i don't think it has "shorted" through. Have these got slip rings or brushes? and could the brushes be seized in their holders? It is a shame if it has to come off again, are the diode packs replaceable in situ (external) or is it a removal and strip down job? Thanks again.Tony
Tony :England:
(providing support for a friends 1972 series 3 V12 2+2)

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Re: Non charging s3 alternator

#5

Postby SRK » Fri Jun 16, 2017 12:14 pm

Tony, the red plastic thing on the back is your brush holder and I have been told you can do both the brushes and diodes in place. For me however I always find it easier to take things like this off the car so I don't mess something else up!! Other than the inside pivot bolt where you have to be a little bit of a contortionist, the alternator is easy to remove and replace. Also, when I did mine I was told you have to "wake up" the alternator which I never quite figured out. After I installed my new (rebuilt) alternator it also did not work so I put a full charge on the battery and went for a drive and then magically it all lit off and has been fine ever since. (I would not get to far from the home however :bigrin: )

Steve

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Re: Non charging s3 alternator

#6

Postby teegee777 » Mon Jun 19, 2017 2:47 pm

Well, I think we have done all the checks and the alternator will have to come off the car and either be dismantled and checked further by us or go back to the repair shop. I did try a known good earth (- ve) on the regulator plug shorted to F and the ignition light was brighter but still not charging. I assume that the regulator -ve may be slightly dirty/corroded which is why it was brighter straight from the battery. I have included an "assumed" wiring diagram below,as it was becoming difficult to understand all the wiring information. I think the main issue was that they were calling the three diodes "field diodes" and not the triple diode?
Image

I also had a small issue with this statement in the manual "Before testing the regulator in detail because of low voltage output, first remove the plug from the regulator and join together negative and field leads at connector plug; do not use the regulator terminals to join the leads together as a short may exist inside the unit. This enables the alternator to run full field and should the fault persist, it cannot be the regulator unit.

Test on the Car
Assuming that the fault persists, check the voltage adjustment setting."

I think that last line would read better if it said "If the alternator is not faulty and assuming that the fault persists".

So the car passed it's MOT and the owner made it to the local car show, however we have a major issue with overheating so will probably start another thread. Is S3 the best section or technical?
Simon, you did some great advertising for the ebay company, they've suddenly all sold out of the triple diodes.
Thanks again to Steve and Simon.
Tony
Tony :England:
(providing support for a friends 1972 series 3 V12 2+2)

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Heuer
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Re: Non charging s3 alternator

#7

Postby Heuer » Mon Jun 19, 2017 4:03 pm

Are these any help from our Knowledge Base?
Lucas Alternators: https://www.dropbox.com/s/c5ype28z7mgpi ... s.pdf?dl=1
Lucas Alternator & Distributor Parts: https://www.dropbox.com/s/zrb0jrxrvru2i ... N.pdf?dl=1
David Jones
S1 OTS OSB; S1 FHC ODB

Pin your E-Type to our World Map: https://www.zeemaps.com/map?group=184509

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vee12eman
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Re: Non charging s3 alternator

#8

Postby vee12eman » Tue Jun 20, 2017 8:51 am

Hi.
Glad to be of help. I have found actual wiring diagrams for both Butec alternator and regulator online, if you want I can look agin. Also, the triple diode is available again from the same eBay seller. I am pretty sure the triple diode is the "field "diode in your picture.

Up to you where you ask technical questions about the car, but avoid duplication if you can, some get a little annoyed!! However, if you post in the technical forum make it very clear it's a Series 3 V12, or people will get confused. There is quite a lot already posted on cooling the V12s on this forum already, have a go with the search facility and you might just answer your questions.

Regards,
Simon S-Y
Series III FHC

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