Yanmar Alternator question


Chris Doucette
 

Good news- 1) the alternator lives to be replaced another day. 2) Another mystery part identified (diode)

After troubleshooting- My alternator tested 14.2v well at the alternator posts but not at battery-  it turned out there is a confluence of wires at the starter post and this post nut was loose- tightened and all was good!  


Dean Gillies
 

I agree with Alan.  This device can also help to reduce conducted or radiated radio frequency interference by suppressing voltage spikes during normal operation of the alternator. That may be important if, for example, the SSB radio is being affected by noise from the alternator. 
--
Dean Gillies
SV Stella *****,  Amel 54-154


Alan Leslie
 

It's probably a Tvs diode,  or high current avalanche diode, installed to protect the alternator from a sudden disconnect of the battery.
Alternators generally don't like being disconnected from the battery when they are turning.
Disconnection creates a large voltage spike which exceeds the diode's avalanche breakdown potential and the current is sent to ground thus protecting the alternbator from an open circuit.
Cheers
Alan
Elyse SM437


Eric Freedman
 

That is definitely not from the factory.

By the shape of the heat shrink, it could be a diode, but that makes no sense. Did you cut it open to see what it is?

 

You should have only 3 connections on that alternator.

The indexed plug, the positive connection to the starter battery connection on the engine, ground wire.  Did you look at the ground connection on the alternator to see if it is insulated?

If not possibly the alternator was changed with a non isolated ground alternator and somehow this is a work around.

Also did you trace the ground wire to where it originates?

 

There should also be a wire hanging loose which is used on other boats for the tachometer.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

From: main@AmelYachtOwners.groups.io On Behalf Of Chris Doucette
Sent: Wednesday, July 06, 2022 6:45 PM
To: main@AmelYachtOwners.groups.io
Subject: [AmelYachtOwners] Yanmar Alternator question

 

I believe its time to replace my yanmar alternator-  does anyone know what this wire is between the ground and positive post?   


Chris sm 385 Amarok


Chris Doucette
 

I believe its time to replace my yanmar alternator-  does anyone know what this wire is between the ground and positive post?   


Chris sm 385 Amarok