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Prestolite Leece Neville alternator voltage


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Hi all, 

My Leece Neville alternator is kicking out >15.7 - 17 volts on anything but tick over. I have brand-new starter battery and leisure batteries.   The alternator has a voltage adjustment screw on the regulator.  I have tried adjusting this and it seems to be completely randomly adjusting the voltage   - turn clockwise it rises and then suddenly drops  similarly anti clockwise.  It looks like the previous owner has already played around with it.   The lowest I can get it is around 14.88,  which I am guessing from reading up on it is still too high.  the batteries are full having cruised for 8 hrs yesterday, solar panels etc...  the voltage didn't drop all day.  The Cyrix ct relay has hopefully protected the leisure batteries as it only cuts in beneath 15.7 volts.    

given I think the voltage regulator screw isn't working very well I was thinking about replacing the regulator - anyone know a good place to buy one, struggling to find anything on line in the U.K?  It's an 8rg2043

ANy one had any similar experiences Or advice or thoughts?

will take into a auto electrical place if this isn't a diy job   

 

Cheers tom

 

 

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I don't know much detail about Leece Nevil alternators but if they are traditional 9 diode affairs your symptoms would squire with a blown field diode.

If they are battery sensed the symptoms would also square with a high resistance between alternator & battery or, just about possibly, on the sense lead. Try cleaning and tightening all charging system terminals.

If the Cyrex is a split charge relay of some sort then the symptoms could also be caused by resistive contact if the alternator sense lead is on a different battery bank to the main charging lead.

Now remember I said I have no detailed knowledge about Leece Nevil alternators.

Are you sure you mean 15.7 volts, I would expect 13.7 for the cut in volts for a 12v system and about 12.8 for the cut out. Please read the spec again. At the voltages you mention I think it would have paralleled the banks.

If you have wet open cell batteries AND you check the electrolyte regularly I think 14.88V would be fine and may extend their life compared with 14.4V. I can't be so sure about sealed batteries so in that case you need to find out their gassing or maximum charging voltage.

Did you do your tests at night or with the solar panels covered? If not how can you be sure its not the solar causing the high voltage?

That's all the help I can give, I hope a Leece Nevil expert comes along to help.

 

 

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3 hours ago, Tony Brooks said:

I don't know much detail about Leece Nevil alternators but if they are traditional 9 diode affairs your symptoms would squire with a blown field diode.

If they are battery sensed the symptoms would also square with a high resistance between alternator & battery or, just about possibly, on the sense lead. Try cleaning and tightening all charging system terminals.

If the Cyrex is a split charge relay of some sort then the symptoms could also be caused by resistive contact if the alternator sense lead is on a different battery bank to the main charging lead.

Now remember I said I have no detailed knowledge about Leece Nevil alternators.

Are you sure you mean 15.7 volts, I would expect 13.7 for the cut in volts for a 12v system and about 12.8 for the cut out. Please read the spec again. At the voltages you mention I think it would have paralleled the banks.

If you have wet open cell batteries AND you check the electrolyte regularly I think 14.88V would be fine and may extend their life compared with 14.4V. I can't be so sure about sealed batteries so in that case you need to find out their gassing or maximum charging voltage.

Did you do your tests at night or with the solar panels covered? If not how can you be sure its not the solar causing the high voltage?

That's all the help I can give, I hope a Leece Nevil expert comes along to help.

 

 

Thanks for the response Tony.  Reading the manual the Cyrix  (victron branded) split charge relay cuts out to protect the second battery bank at >15.7v to protect against gassing.   The alternator is connected directly to the starter battery with the isolation switch between the battery and starter motor. The Cyrix relay the cuts in either way when either battery bank is charging. the solar panels are connected to the leisure batteries and in yesterday's sunlight we're getting up 12.9v.    The high voltage readings are from the back of the starter motor.  The starter is a 220amp flooded battery whereas the leisure battery's are 4 x 115amp sealed.  Both fairly sets cheap Avon batteries but brand new.     

1 hour ago, jonesthenuke said:

Leece Neville have a fairly good set of information on their US web pages:-

http://www.prestolite.com/literature/training/PP1127_TrainingManual_lores.pdf

http://www.prestolite.com/literature/tech/alts/PP1154_Flowchart.pdf

 

Hope this helps

Thanks - the flowchart points to replace alternator .  I was hoping to be able to do a diy fix  by replacing the the regulator.   I'll take it in 

cheers tom 

Edited by Capella247
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Following on from those links and a but more internet research it appears that Leece Nevil supply 6 and 9 diode machines so we come back to if yours is a nine (Trio diode pack) machine the fault could be a faulty field diode, but not if its a six diode machine.

I also found this http://www.prestolite.com/pgs_support/volt_install.php that shows some regulators have a movable link thats elects the charging voltage. It would eb best to make sure yous is not like this.

If you know the alternator model and what you are looking at this may help http://www.prestolite.com/pgs_products/piecepart_category_select.php

It maybe worth warning that Prestolite now manufacture alternator designs from a number of manufacturers so the Leece Nevil bit is important so you get info about the correct design.

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On 04/02/2018 at 09:26, Tony Brooks said:

Following on from those links and a but more internet research it appears that Leece Nevil supply 6 and 9 diode machines so we come back to if yours is a nine (Trio diode pack) machine the fault could be a faulty field diode, but not if its a six diode machine.

I also found this http://www.prestolite.com/pgs_support/volt_install.php that shows some regulators have a movable link thats elects the charging voltage. It would eb best to make sure yous is not like this.

If you know the alternator model and what you are looking at this may help http://www.prestolite.com/pgs_products/piecepart_category_select.php

It maybe worth warning that Prestolite now manufacture alternator designs from a number of manufacturers so the Leece Nevil bit is important so you get info about the correct design.

Thank you Tony.   I had a look at the documents you've provide and using a volt meter tried to adjust the voltage regulator.  It is however all over the place and seems to not want to adjust anywhere near 14 volts.  Mostly settling st 16.   I've ordered a new voltage regulator which was £35 plus vat (which seems pretty reasonable) so will see whether that does the trick.

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2 hours ago, Capella247 said:

Thank you Tony.   I had a look at the documents you've provide and using a volt meter tried to adjust the voltage regulator.  It is however all over the place and seems to not want to adjust anywhere near 14 volts.  Mostly settling st 16.   I've ordered a new voltage regulator which was £35 plus vat (which seems pretty reasonable) so will see whether that does the trick.

I think Prestolite discontinued the adjustable regulators based on “user experience” (i.e people messing with them). I’m sure you can still buy the adjustable ones somewhere.

Check the continuity of the small wires passing though the side of the regulator mounting; had one fail, insulation was ok but all the strands of copper had failed, odd as there is no strain on them.

The other area to check is the brush gear if yours has the sealed brush gear compartment, (8MR series) the build up of dust from the brushes as they wear can cause some odd symptoms. Just clean it out with an artists brush if you have this type.

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I have a leece neville alternator all be it with out the adjustable regulator.  I have had "much fun" with it over the years and now know it well. 

It is an 8HLA frame with 140A innards. 

Leece Neville Model No 8LHA2070VA 1-2429-00MO

12v 140a

Regulator – 8RG2112

Rectifier Block -MR6206 1567CM

It is very easy to take apart as the back bearing is held in place in the rear housing with an o ring.  The diode block is bolted in which I had to replace to unit as the diode are welded to the wires.  Much harder than silver solder I was expecting.  Regulator cost about £15 Diode block on aluminium heat sink about £35.

Regards

Graham 

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15 hours ago, Eeyore said:

I think Prestolite discontinued the adjustable regulators based on “user experience” (i.e people messing with them). I’m sure you can still buy the adjustable ones somewhere.

I think users were adjusting voltage too high and damaging alternator, I'm guessing they didn't wait for charge voltage to level out before adjusting it.  I had to replace our large frame Leece Neville, the new one came with non adjustable reg so I replaced it with the old one. 

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  • 9 months later...

So picking this up again as the title of this thread is still accurate and the - earlier this week the same leece neville alternator packed up completely - no charge.   Replaced the regulator (bought in February and has worked fine since) on Thursday and it had been fine until today, when once again it has packed up.   Nothing has changed with the rest of the wiring so anticipate something else within the alternator is causing the problem.  Its just odd that it worked ok for a couple of days and then packed up again today.    I don't want to replace for the regulator again for it to fail again as it is likely not to be the cause of the problem - does anyone have any ideas about what could be causing the regulator to fail like this?  Is it likely to be the alternator or something else?  Nothing else within the engine electrics has changed.

 

Tom

 

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  • 1 year later...

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