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Old 20-09-2020, 07:21   #1
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Installing new alternator

The alternator that came with the boat did not fit right, so used odd sized belt and burnt through them quickly. But it did work.
I bought a 55 amp alternator sized for my engine. 3gm30 yanmar from 1992.
The wiring connections are different, but by my research it is wired correctly. Unfortunately it doesn't charge. Testing at the alternator, and victron monitor both show same battery voltage before and after starting. 12.5 volts on this last test.
I think the internal regulator is no good, and I have an extra for the other engine, but want to get advice before swapping it out. In case I'm doing something wrong. Yes, basically second guessing myself.
My key switch, through the dummy light routes through the 2 wire plug,(light comes on with key and turns off when running) and 12 volt goes to the terminal shown.
Pictures are of the spare for easy viewing.
Also pic of the old one taken out
Any help would be apreciatedClick image for larger version

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I also tested that it is grounded well through the motor
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Old 20-09-2020, 08:02   #2
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Re: Installing new alternator

Correction. The key loop gets 12 volt when key turns on. Light does not go. So I have to chase that down.
The light my wife said came on is the oil light
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Old 20-09-2020, 09:10   #3
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Re: Installing new alternator

Without trying to thread my way through the wiring, it sounds as if you are not sending voltage to the field. Without that electromagnet getting voltage, no current out the other end. There are others with a more sophisticated knowledge thereof who hopefully will chime in.
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Old 20-09-2020, 11:21   #4
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Re: Installing new alternator

The light stays on because something is wrong inside the alt.

Yanmar normally has 2 small wires. A blue and red. One is key power and one is lamp. Both should be plugged in to those 2 terminals. Do you only have 1?

I can’t recall which color is which or which pin is which.
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Old 20-09-2020, 11:48   #5
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Re: Installing new alternator

Quote:
Originally Posted by smac999 View Post
The light stays on because something is wrong inside the alt.

Yanmar normally has 2 small wires. A blue and red. One is key power and one is lamp. Both should be plugged in to those 2 terminals. Do you only have 1?

I canít recall which color is which or which pin is which.
I wrote that wrong. Light does not go on period. It did with the old alternator, so I have to chase wires now.
It has been altered and rewired by Po's to the point that wire color doesn't help unfortunately.
Next year we plan an engine overhaul with new panel and harness. So that will get things back to proper. But need to get some power for this year in the mean time
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Old 20-09-2020, 12:45   #6
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Re: Installing new alternator

If you have the 55A Hitachi alternator installed you can test it without bringing it to a shop.

The two blade terminals on the back of the alternator are, looking from the rear, top blade is horizontal it's your battery sense voltage reference for the internal voltage regulator. The lower blade, the vertical one, is the key ignition loop that is feed through the charging indicator light or a 10 ohm, 10 watt resistor.

So to test the alternator you need to install a 10 ohm resistor in the vertical blade feed. I single wire from the battery that feeds the horizontal blade and then feeds the vertical blade through a 10 ohm resistor is all you need to fire it up and test. If the alternator works then you need to chase down the wiring from the ignition switch to the alternator. But for final wiring I would keep the battery sense wire to the horizontal blade independent from the ignition switch.
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Old 20-09-2020, 15:21   #7
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Re: Installing new alternator

A note. The alternator light bulb in the older Yanmar panels is a different bulb than the similar-looking ones used for the alarm lights. They are not interchangeable. IIRC when that bulb goes out, the alternator doesnít work.
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Old 20-09-2020, 17:25   #8
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Re: Installing new alternator

FWIW, this is how Yanmar wires up the 55 Amp Hitachi alternator.
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Old 20-09-2020, 17:39   #9
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Re: Installing new alternator

A couple of stupid things, adding here just for completeness:

1) Sometimes you have to wait a minute and/or throttle up a bit, before the alternator "kicks in."

2) If you've upgraded, be sure the wires are adequate and connections are good. I recently burned up a wire after missing this step.

Either of these may or may not apply here. If not, please ignore.
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Old 21-09-2020, 07:42   #10
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Re: Installing new alternator

I've been studying the Po's schematics from 97. I have the blue black wire(lb) but not the red black(rb)
Positive and ground are good.
Just need to figure out whatever has been switched for rbClick image for larger version

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Old 21-09-2020, 08:22   #11
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Re: Installing new alternator

Look at the schematic Wotname provided. they are both switched. One wire going through the charge lamp the other doesn't. The one that doesn't is the voltage reference lead for the internal regulator. A very poor way to supply reference voltage IMO. But that is the only way that engine manufacturers can supply plug n play wiring.

As I mentioned in an earlier post, you can bypass all the current wiring to test the alternator but you do need to use a resistor in the wire to the lower, vertical blade.
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Old 21-09-2020, 10:04   #12
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Re: Installing new alternator

Quote:
Originally Posted by kenbo View Post
Look at the schematic Wotname provided. they are both switched. One wire going through the charge lamp the other doesn't. The one that doesn't is the voltage reference lead for the internal regulator. A very poor way to supply reference voltage IMO. But that is the only way that engine manufacturers can supply plug n play wiring.

As I mentioned in an earlier post, you can bypass all the current wiring to test the alternator but you do need to use a resistor in the wire to the lower, vertical blade.
The marina close to us is open today, I'm headed in to try and get a resistor. And a 9volt battery so I can get my wire tracer working again.
Just to be clear on the test, I run 12 volt + to the horizontal blade, then jumper from it through the resistor to the vertical blade? Or 2 separate wires from 12volt + with the resistor in line to the vertical blade
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Old 21-09-2020, 10:42   #13
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Re: Installing new alternator

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Originally Posted by chris mac View Post
The marina close to us is open today, I'm headed in to try and get a resistor. And a 9volt battery so I can get my wire tracer working again.
Just to be clear on the test, I run 12 volt + to the horizontal blade, then jumper from it through the resistor to the vertical blade? Or 2 separate wires from 12volt + with the resistor in line to the vertical blade
Either way works, what ever is easies for you. And you have the blade functions correct as well. Good luck!
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Old 21-09-2020, 14:50   #14
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Re: Installing new alternator

Hmm... I would strongly advise the wire going from or to the resistor (or lamp) be switched by the key (ignition) switch.

This wire (which goes to the L termination) provides the initial excitation voltage for the field. If left unswitched, the field current will flow even when the alternator is stationary.

I can post the internal wiring of the alternator if you need it.
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Old 21-09-2020, 15:02   #15
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Re: Installing new alternator

FYI on Hitachi alternators:


Hitachi/Yanmar Alternators: (by Maine Sail)

Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop. Actually, to the alternator, they are pretty smart but to your batteries and the speed of charging they are flat out stupid. Why?

Hitachi alts with dumb regulators, and some others, limit voltage but also reduce voltage based on alternator temperature. This is a self protective feature installed in the internal dumb regulator to prevent the alternator from cooking itself. Remember voltage is the pressure that allows more current to flow. So, if we reduce the absorption voltage, then we also reduce the current the alternator is supplying.. Any battery at any state of charge simply will not accept the same current at 13.4V that it did at 14.4V and as a result the alternator will run cooler. What do you suppose this does to your batteries over time.......?

The problem is that when cold you will get 14.3V to 14.4V out of the Hitachi but as the alternator heats up the dumb regulator begins to reduce the CV/voltage limit based on the alternators internal temperature. It is not uncommon to find a Hitachi alternator at 13.4V when hot. This is REALLY, REALLY DUMB....

If you have a dumb regulator, and notice the voltage dropping, it is likely a temp compensated dumb regulator. Get rid of it or plan to buy new batteries more often.

If you have a temp compensated alternator or a Hitachi alternator on a Yanmar you really are in dire need of external regulation if deep cycling a larger battery bank.

This is from:

http://forums.sbo.sailboatowners.com...d.php?t=125392

and these, too:

http://www.cruisersforum.com/forums/...on-125843.html


http://www.cruisersforum.com/forums/...or-142083.html
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