Disabling an alternator

[catmandoo]

seems like using a sledgehammer to crack a nut

 

[cindersailor]

I had a similar problem when I fitted a 60A alternator to my 6.5 hp Yanmar 1GM. In particular I wanted to be able to disable the alternator without having to stop the engine first in situations where I suddenly needed all power to the prop. Take a look at the thread I initiated at the time (http://www.ybw.com/forums/showflat....ds=cindersailor&topic=&Search=true#Post429824)

I fitted a simple toggle switch into the field exciter wire and it worked perfectly; on-off-on-off as many times as you want at the flick of a switch with no damage to the alternator over 2 years.

 

[bluedragon]

Thanks Cindersailor...I didn't find this in my original search, but found the replies you got most helpful. When you say the field exciter, I presume you mean the connection between the voltage regulator and the field coils, not the warning light excitation circuit?

If so, now all I need to do is pull the back off the alternator and find the field coil wiring!! Well most of what I learnt as a kid was from "mess with it until it breaks, and then learn how to fix it"...but hopefully I've become a little smarter since then

 

[VicS]

The field current is fed to the rota via the brushes and slip rings so a switch in the the wiring to the brushes will do the trick. BUT some alternators have the brushes combined with the regulator. If that's the case it is not going to be so simple. Maybe you will then have to interupt the circuit between the diodes (rectifier) and the regulator but some excitation will still occur via the warning light which will glow brightly. Perhaps it will be necessary to use a double pole switch to interupt the warning light circuit at the same time.

 

[cindersailor]

Yes thats right, fortunately on my alternator this was a separate external wire but some alternator designs may have this buried internally somewhere.