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Old 30-06-2016, 16:25   #1
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Yanmar 3GM30 alternator wiring....

Am I correct in deducting that if you turn the ignition switch off whilst the engine is running all it does is de-excite the fields of the alternator hence
no charging? 3GM30 has manual fuel cutoff.
Then the engine alarm circuit has no power either?
Any other pitfalls for doing this?
Ta.
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Old 30-06-2016, 18:30   #2
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Re: Yanmar 3GM30 alternator wiring....

Should be easy enough to determine with a volt meter; with the engine off disconnect the field wire, hook up the voltmeter, and turn the switch on and off. All my ignition switch does in the on position is power the gauges. Yours may power the field, but it can't do much more than that, since the diesel doesn't need it once it's started.
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Old 30-06-2016, 18:39   #3
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Re: Yanmar 3GM30 alternator wiring....

Thanks for the brain jog.
Of course, it wont even stop charging as the the fields are internally excited once the engine is going.
I need to isolate the fields with a switch as protection against overheating battery and alt.
Delco clone 10si
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Old 01-07-2016, 03:56   #4
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Re: Yanmar 3GM30 alternator wiring....

Depends on your alt. The original Hitachi alt is internally excited. I disabled that and put in an external field wire to work with my Balmar reg (also had to convert the alt to +field control). But my Balmar reg is powered by the ignition anyway, so turning the key off kills power generation by killing the reg. And alarm lights and buzzer go away, too.
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Old 01-07-2016, 13:12   #5
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Re: Yanmar 3GM30 alternator wiring....

I'm keeping my Hitachi 55A as backup and pulling in its place a 120A delco clone with a larger diameter pulley as it may eat V belts otherwise.
Factory pulley is around 80mm.
I wanted a 100A but no "bolt ons".
Easy to switch fields by cutting earth tab on brushes & putting a switch to earth.
Also, putting temperature sensing audible alarm on alternator.
How hard was it on the hitachi?


Endurant R232 x4= 464Ahr @12V
Hitachi 55A
250W solar gathering dust in back room.(Soon to see sunlight.)
NZ Smart charger ZM4 in the wings.

My hitachi does 36A for 5mins @75% soc.
Then ----> to 8 amps within half an hr.
The 10si was $75 us. I am curious to the performance/longevity.
Two yr warranty!
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Old 02-07-2016, 08:04   #6
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Re: Yanmar 3GM30 alternator wiring....

I used an Hitachi knockoff and switched it to P field by straightening the -brush tab and moving it from the F pole of the IR to ground pole. Removed the triple pack diodes. +brush is still connected to Lamp, so I used that for field. No soldering, no additional wires, can be easily put back.
Balmar reg provides lamp output for alarm conditions.
Tach output still works, not needed for Yanmar.

Works great, but temperature sensing for batts and alt is essential.
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Old 02-07-2016, 13:41   #7
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Re: Yanmar 3GM30 alternator wiring....

Quote:
Originally Posted by becrux View Post
I used an Hitachi knockoff and switched it to P field by straightening the -brush tab and moving it from the F pole of the IR to ground pole. Removed the triple pack diodes. +brush is still connected to Lamp, so I used that for field. No soldering, no additional wires, can be easily put back.
Balmar reg provides lamp output for alarm conditions.
Tach output still works, not needed for Yanmar.

Works great, but temperature sensing for batts and alt is essential.
Thanks! Great info on your experience.
Went to the boat yesterday to do the biz but as usual ducks wouldn't line up.
Hitachi pulley wouldn't come off to swap, and the factory pulley was 3/8.
Why they supply a 120A alt with a 3/8 pulley beats me.
Doesn't bode well.

So went up the mast instead.
Junk yard diving today.
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Old 03-07-2016, 01:16   #8
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Re: Yanmar 3GM30 alternator wiring....

I hear you on the hard-to-remove pulleys - and why "3/8"?
Impact wrench air drive is the way to go. Like at the tire store. Comes off easy.
Also, got some blue kevlar belts from vbeltsonline (or something very like that) that seem not to slip as much. Got 4 for about $32 or so. Belts were < $6, but they charge for shipping.
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Old 03-07-2016, 01:25   #9
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Re: Yanmar 3GM30 alternator wiring....

Forgot you were in NZ. The belts are great if you can get them.
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Old 03-07-2016, 02:02   #10
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Re: Yanmar 3GM30 alternator wiring....

Hard enough getting green stripe gates, "off the shelf".
Guess I would have to order from Vbeltsonline direct, which isn't a problem
these days. Probably get here faster than ordering from within NZ.

So, you have found the kevlar ones last longer than the cogged?
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Old 06-07-2016, 03:04   #11
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Re: Yanmar 3GM30 alternator wiring....

Haven't put on enough hours to know. But they seem pretty grabby. No dust yet.
BTW, if you got the same alt I did from dbelectrical, you'll need a 39" belt. The old 38 won't make it, and 40" is too big. 39" is Goldilocks.
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Old 06-07-2016, 03:18   #12
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Re: Yanmar 3GM30 alternator wiring....

Couple more things:
That alt will get pretty hot pretty fast if your batts are down, especially if an external reg is trying to drive it hard. Temp sensing is vital, and probably dialing back the reg. A good supply of cool air would help.
I haven't used the internal reg, so I don't know how well it does temperature compensation.
Fire me a PM when you want to convert it for external reg.
I have pictures.
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Old 06-07-2016, 12:09   #13
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Re: Yanmar 3GM30 alternator wiring....

Quote:
Originally Posted by becrux View Post
Haven't put on enough hours to know. But they seem pretty grabby. No dust yet.
BTW, if you got the same alt I did from dbelectrical, you'll need a 39" belt. The old 38 won't make it, and 40" is too big. 39" is Goldilocks.
You read my mind and it, corresponds with the measurement I just took at
1000mm=39.37".

Do you take the water pump pulley off to get the belt on? As the new 120A has to be pivoted right down against the oil filter to get that dimension?
My alt pulley is 98mm O.D.

Awesome, BC, as its a PIA kayaking out to the boat if I make a mistake.
Great to have it corroborated.
This forum is the best!

Yeah, on the heat. That why I derated it with the bigger pulley. I'm giving it extra air externally for the lower alt. rpm's.
At this stage I will try the internal reg and see how it copes. (With temp alarm) but may take you up on the procedure if I get a balmar reg.
At this stage I would rather weld up the solar arch/dingy davit than and get the solar online.
Limited time, low funds.
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Old 07-07-2016, 10:49   #14
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Re: Yanmar 3GM30 alternator wiring....

The bigger pulley might make it harder to use a 39" belt. I don't have to do anything special to put it on.
Also, the kevlar belts don't seem so wonderful right now. Seem to be wearing quickly.
So many projects - so little time.
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Old 08-07-2016, 14:54   #15
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Re: Yanmar 3GM30 alternator wiring....

I couldn't get a kevlar, off-the-shelf, so went with bosch and a gates green stripe as backup. Then might try some optibelts XPA next.

New alt. not charging. Doing diagnostic today.

Any body know what this fourth terminal is. Presume tacho?
Any test to confirm? My tacho is magnet/flywheel driven.
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