If your alternator is not working then you should simple get an alternator buzzer alarm.
This assumes your alternator alarm is working. When you turn your key on to provide power before actually cranking the engine the engine, you should hear the buzzer and see possible two lights on. If you don’t have lights, you can disconnect the wire on the engine oil pressure switch. The pressure switch provide alarm ground when there is no(or low) pressure. Unplug this wire and keep it from grounding against the engine block and turn the key on, if you get a buzzer then the alternator alarm is working. Some of the confusion regarding killing or not killing an alternator may likely stems to the the type of alternator and how it’s connected. Most Yanmars come with internally regulated Hitachi alternators. Maine Sail called these alternators “ dumber than a pound of beetle poop”. My old C&C 29 had the standard 35A Hitachi. The key switch would only provide 12V power to a line through an alternator alarm buzzer then to the alternators “lamp” connection. When the alternator was not spinning, the “lamp” connection provided the ground for the buzzer to alarm. When the alternator was spinning and working, it provided 14V at the “Lamp” connector and since it was also providing 14V to the battery, the alarm buzzer saw 14V before and after (i.e. zero volt difference) and stopped buzzing. The alternator also had a connection (top of T-connector) for the battery sensing used by the internal regulator. In this case, the sense was connected via a short loop to the battery connection. So for this arrangement, I would guess that shutting off the key switch would not harm the alternator. And I know from experience this to be the case. I have heard that some old internal regulated alternators do not have a sense connection but rather likely use the lamp connection for sensing. Or maybe even some sense connections are connected to the a key powered switch. In these cases, I could see how an alternator could be harmed by a sudden disconnect of the sense voltage. - Paul E. 1981 C&C 38 Landfall S/V Johanna Rose Carrabelle, FL http://svjohannarose.blogspot.com/ > On Jul 20, 2016, at 12:00 PM, [email protected] wrote: > > Date: Wed, 20 Jul 2016 08:54:27 -0600 > From: Lorne Serpa <[email protected] <mailto:[email protected]>> > To: [email protected] <mailto:[email protected]> > Subject: Re: Stus-List Relocating the Yanmar key now alternator.. > Message-ID: > <CAL=lx5v_6uo_r-ieuxmgm4ahmaw_bbxjgs5q2ytjtpzr-dp...@mail.gmail.com > <mailto:CAL=lx5v_6uo_r-ieuxmgm4ahmaw_bbxjgs5q2ytjtpzr-dp...@mail.gmail.com>> > Content-Type: text/plain; charset="utf-8" > > Hum, I. New to this boat and boats with diesel engines. Numerous times > past couple weeks have turned key off without killing the engine. I have a > 20gm. How do I know if I did damage? Check battery voltage while engine is > running? Should be 13.5 or so? > > Lorne Serpa > C&C 30MKII 1988 > Friendship, MD > On Jul 20, 2016 12:50 AM, "Leslie Paal via CnC-List" <[email protected] > <mailto:[email protected]>>
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