Yanmar 24 volt alternator make/model

Alan Leslie

Well done !
Elyse SM437


Dear all,

I have finally fixed the alternator problem, and it was not really straight forward;

After knowing about the relay and the red light in the 24 volt panel, I soon discovered that the circuit for exiting the 24 V alternator and lighting up the red light was not correctly installed.

There was one wire connected to the + terminal of the alternator, this small gauge wire was moved to the "F" terminal of the alternator, and now the red light works as expected (lights up when ignition "ON" and turns off when motor starts and alternator delivers power).

Thank you for all the input, your help was crucial for me finding the fault and correcting the problem!

BR Niels


To me, the red light on the 24V panel just means the alternator is not providing a charge.

For instance, in our case this happens every time in the 5-second period between turning the engine on and the external Mastervolt regulator telling the alternator to, well, start charging the battery.  This delay is programmable and we've never bothered changing it.


SM2K Nr. 350
At anchor, Le Grazie (La Spezia)

Alan Leslie

According to my manual....

The red indicator (bottom left) being on, shows a fault (loose or broken belt, too low rating (?), faulty regulator) on the 24V alternator.
This indicator can also be lighted if all the chargers and alternators are working simultaneously(the alternator measures an high open voltage and so stops charging)

Elyse Sm437

amelliahona <no_reply@...>

Am I missing something here?  On my SM (Hull #335) the red lamp in the lower right hand corner of the 24 VDC panel  illuminates red when alternator output voltage is less than battery voltage and extinguishes when adequate RPM is generated to raise the voltage to a battery charging voltage.  I believe it is a voltage base warning lamp and not a current based lamp but I haven't studied it in detail.  In all that has been written I haven't seen anybody suggest some basic trouble shooting like checking for voltage on the field wire, (forgive me if I am wrong since this is such a lengthy thread).  I'll have to do a little research on the involved circuits to verify.

All the best, 

Gary S. Silver
s/v Liahona
Amel SM 2000 Hull # 335
Puerto Del Rey, Puerto Rico

John Clark

Congratulations on the purchase Niels,

Bigouz looks like a very fine vessel...I had it on my "short list,"  I guess I was too slow for you speedy Danes!   ;)

                     Regards,  John

Alan Leslie

Hi Neils,
The 24V alternator is a Leece Neville 8SC 175A alternator with an inbuilt regulator, unless a previous owner has modified it like ours to have an external regulator.
How do you know that its not charging? No amps on the Xantrex monitor ?
If the red light isn't on then maybe you have an issue with the connection between the alternator output and the batteries.
I would check all the connections, particularly the heavy cables for tightness first.
Then use a multimeter to check the voltage at the alternator across the big cables when the motor is running.
If its over 28 volts then the alternator is working, if its not then the re is an issue with the alternator...and it maybe be only the regulator, which is replaceable.
Go to the Leece-Neville alternator page for this model 8SC,
Prestolite - Leece Neville


there's a lot of information there .....
Elyse SM437

Niels Hauerslev <niels.hauerslev@...>

Hi, as a new owner, I am having trouble with the 24 Volt alternator not charging.
The red lamp on 24 Volt panel does not light up at any time, showing fault, so tried to hook up a 24 Volt G4 bulb to the "red light" wires, just to check if the lamp was OK, but still no light comes on...
Does anyone know the make/model of the 24 Volt alternator, sitting on the Yanmar 4JH on a SM2000?? I think I will get a new one, and get the old one repaired for spare. The sticker on the alternator is gone.
Thanks a billion!
Bigouz SM2000 #351