Re: [Amel Yacht Owners] Alternator and Masse leak detector

ngtnewington Newington

Hi Alan,

Thanks for your input on this. I have just had a long conversation with the Leece-Neville distributor here in the UK. 

I described all the symptoms you know about, and that I have raised over the last six months on this forum. He said that, he has seen this before on Leece-Nevilles and in his opinion there would probably be one diode not working properly and at low rpm the Alt would not work as it was kind of missing a beat but as the rpm increases the alternator gets over the missed beat and starts to charge but probably only at 50% of its potential output running on the remaining diodes.

 As for the leak, he agrees with your opinion that it would not be from a faulty diode and that most likely one of the insulating washers had perished or a build up of some debris was bridging from the negative side to the frame. He advised me to consider a brand new alternator that he had in stock that is exactly the same as the old and would throw in the smart regulator set for AGM's and wire it up for me prior to shipping for free.. The double pulley is the same, I only must check the rotation for the fan as it is clockwise as you look at it from the pulley end. If necessary I can take the fan from the old one, but I think they are exactly the same.

So this is what I will do, after all the old one is 12 years old, and then get the old one checked and serviced and keep for spare.  He completely agreed that the bridging to the frame would not stop it working and that also a defective diode would not stop the alternator from working all be it at higher rpm and at a lower output but the bridging could cause  galvanic corrosion problems.

So in conclusion to other Amel owners if your 24v alternator only works at higher rpm you should check that it can put out it’s full rated output. If not have it serviced you may have a dodgy diode, and frankly if there is a bad diode it is likely there may be other damage too as with mine.


On 20 Jun 2018, at 08:31, divanz620@... [amelyachtowners]> wrote:

Hi  Nick,

Agree you found the "fault". 
It is the alternator.
BUT I very much doubt that it is a diode "leaking" to the frame.
It's more likely to be a breakdown in the insulation could even be something as simple as salt crystals around the negative terminal providing a circuit from  -ve to the alternator case.

Good luck
Elyse SM437

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