Wiring a new alternator (Yanmar)

[Leif-J]

Help please!
Purchased a new(ish) alternator from a forumite, and as it is a bit different from the original, I am at a loss how to connect this correctly.
Engine is Yanmar 3GM30F, and the original alternator is the one to the right in attached photo.
My suggestions to wire the new one are based on pure guessing. I am especially unsure of the function of the loose wire in the middle.
Am sure there are some of you laughing now but better safe than sorry - do not want to blow up anything!

Now hope the photo gets uploaded correctly - realize that the small size file allowed does not make it easier to read texts. They are from left to right:
Plug - Red wire?? - What to connect here?? - Black wires?? - Black wires (2 together) - Plug - red wire (assume +)

 

[Leif-J]

Better photo

Maybe this photo is better to see.

 

[VicS]

You dont tell us the make of the new one.

The new one may have a connection for a rev counter .


If nobody can tell you for sure maybe take the new one along to an auto electricians .. ask them to identify the terminals for you. Maybe get them to test it.

 

[Billjratt]

Are they direct equivalents? The hitachi looks as if it may have an isolated return (negative) - is there an insulator under the nut?
What type is the new alternator - I can't see ANYTHING written on it!
The positive (red wire) screw terminal will be connected to one of the two spades in the plug internally - you can measure with an ohm-meter. I think it should possibly be the one that is in the circular shield thing - the other looks like a chassis/negative in the picture.
Give us details of the new one - make model, and we/you can google for more info.
Make sure you get it right before connecting!
Not sure about the other components on the exterior of the new alt -sometimes splitters were fitted and of course the raw AC for a tacho connection. If you didn't already use these connectors they are not important at this time.

 

[VicS]

I have this diagram of the wiring of a Hitachi alternator. May be useful maybe not.

P is the tacho connection.

 

[Mistroma]

VicS diagram looks as I'd expect it. I was planning to swap over my alternator (existing one looks very similar to your new one). Unfortunately the diagrams and manuals are still on the boat in Spain.

I remember looking at the Yanmar workshop manual and seeing that the external wire went to the IC regulator + other oddities. I didn't believe this and as far as I can remember:

The external wire went to the tachometer
The plug in wires went back to the igniition light and start/stop switch
The alternator was isolated and so had a sep. -ve connector

Sorry that I can't publish pictures, diagrams and details. Hopefully the diagram supplied by VicS will be sufficient. I might have a copy of the page from the Yanmar manual but am pretty sure it didn't look correct (based on my memory of tracing everything back on Jeanneau's wiring diagram and physical checks).

 

[Leif-J]

I have this diagram of the wiring of a Hitachi alternator. May be useful maybe not.

P is the tacho connection.

Thanks Vic.
Tacho I do not need. So "all" I have to do is identify + and E - but that is my problem.
It is now at the boat, so cannot see details on make and number, but I have assumed all along that it is Hitachi as came as original mount on another Yanmar engine (more recent model than my 3GM30F from 1995).