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Old 14-08-2019, 16:26   #1
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Help needed with alternator replacement on a Yanmar 2gm

Ahoy Mates - I have to replace the old Hitachi LR 135-31 alternator (internal regulator) on my Yanmar 2gm and need help with the wiring. I have 3 terminals - B, L, E (from left to right)plus a wire coming out of the alternator case.. My problem is that the replacement alternators have a completely different terminal setup so I need to know where the wires that are attached to the old alternator go on the new one. the picture of the old one.
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Old 14-08-2019, 16:49   #2
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Re: Help needed with alternator replacement on a Yanmar 2gm

Possible replacement
http://www.cruisersforum.com/forums/...1&d=1565822887
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Old 14-08-2019, 17:17   #3
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Re: Help needed with alternator replacement on a Yanmar 2gm

Find out if the new alternator is internally or externally regulated.


If externally regulated you need a regulator and need to change your wiring around


If internally regulated then it goes like this--



Old B goes to new Bat
Old E goes to new E. This is the ground

Old L goes to the bottom of the "T" on the "T" shaped connector.

Cross of the "T" on the "T" shapped connector should be jumpered to "Bat". It is the voltage sense lead.


Wire sticking out of the case is probably a tachometer lead and you'll have to do without
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Old 14-08-2019, 17:25   #4
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Re: Help needed with alternator replacement on a Yanmar 2gm

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Originally Posted by Kidd Karibe View Post
Ahoy Mates - I have to replace the old Hitachi LR 135-31 alternator (internal regulator) on my Yanmar 2gm and need help with the wiring. I have 3 terminals - B, L, E (from left to right)plus a wire coming out of the alternator case.. My problem is that the replacement alternators have a completely different terminal setup so I need to know where the wires that are attached to the old alternator go on the new one. the picture of the old one.
Why not just have the old one rebuilt?
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Old 14-08-2019, 17:41   #5
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Re: Help needed with alternator replacement on a Yanmar 2gm

Page 12 ➥ http://svpegasus.org/wp-content/uplo...5-15-21-32.pdf
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Old 14-08-2019, 20:59   #6
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Re: Help needed with alternator replacement on a Yanmar 2gm

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Why not just have the old one rebuilt?
Uncle Bob - I tried that but it only worked for about 1/2 hour, 40 years old and it is worn out, the case is shot, so replace is the only option now. Thanks for the reply, much appreciate all the help I can get.
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Old 14-08-2019, 21:04   #7
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Re: Help needed with alternator replacement on a Yanmar 2gm

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Thanks for the link, much appreciated !!
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Old 14-08-2019, 21:06   #8
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Re: Help needed with alternator replacement on a Yanmar 2gm

Quote:
Originally Posted by Jammer View Post
Find out if the new alternator is internally or externally regulated.


If externally regulated you need a regulator and need to change your wiring around


If internally regulated then it goes like this--



Old B goes to new Bat
Old E goes to new E. This is the ground

Old L goes to the bottom of the "T" on the "T" shaped connector.

Cross of the "T" on the "T" shapped connector should be jumpered to "Bat". It is the voltage sense lead.


Wire sticking out of the case is probably a tachometer lead and you'll have to do without
Thank you for the info, hopefully whatever alternator I get will have the markings.
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Old 15-08-2019, 10:39   #9
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Re: Help needed with alternator replacement on a Yanmar 2gm

Quote:
Originally Posted by Jammer View Post
Find out if the new alternator is internally or externally regulated.


If externally regulated you need a regulator and need to change your wiring around


If internally regulated then it goes like this--



Old B goes to new Bat
Old E goes to new E. This is the ground

Old L goes to the bottom of the "T" on the "T" shaped connector.

Cross of the "T" on the "T" shapped connector should be jumpered to "Bat". It is the voltage sense lead.


Wire sticking out of the case is probably a tachometer lead and you'll have to do without
re tachometer lead. this lead is connected to one of the alternator's stator outputs [ahead of the internal rectifying diodes] and provides an AC signal for a remote tach. it is possible to purchase an alternator with this stator tap if having a tach is important. the AC frequency [as used by the tach] depends on the rotational speed of the alternator, and this speed depends on the alternator pulley size and engine speed. in most cases, you can reuse the pulley from the old alternator if the pulley diameter on the replacement is different.
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Old 15-08-2019, 10:49   #10
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Re: Help needed with alternator replacement on a Yanmar 2gm

"Cross of the "T" on the "T" shapped connector should be jumpered to "Bat". It is the voltage sense lead."

For best results, the voltage sense wire should go back to the battery or ignition switch rather than just being connected to the Bat or B terminal on the alternator. If you use a current carrying cable such as the Bat or B terminal wire, there are resistive and inductive voltage variations depending on changing current loads. These voltage variations prevent accurate regulation.
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Old 21-08-2019, 17:43   #11
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Re: Help needed with alternator replacement on a Yanmar 2gm

This is the alternator that I ended up ordering. It has an internal regulator.
Looks pretty straight forward to wire Old B to Bat, old E to E, old L to the bottom spade of the T shaped terminal and tach wire to the wire on the side of the new alternator.. Will I need to run a wire from the Top spade of the T shaped terminal to the battery for the voltage sense ?? The old alternator (See pic above) did not have a wire like that, but it might have been internally hooked to the B lead - not sure about that. All help much appreciated and needed too (:>) Also I have no idea what the 2 wires that were hooked to the L terminal on the old one went to, but figure if I hook them up to L again should be ok. All thoughts on that appreciated too !!
Currently we (boat & me) are in Mexico in a small port and no local expert help available so the help you folks give me is so needed, waiting 2 weeks for amazon to get the alternator here and sure don't want to hook it up wrong.
Thanks again to all. [IMG]www.cruisersforum.com/gallery/showimage.php?i=13843&c=503][/url][/IMG]
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Old 21-08-2019, 18:09   #12
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Re: Help needed with alternator replacement on a Yanmar 2gm

Quote:
Originally Posted by Kidd Karibe View Post
This is the alternator that I ended up ordering. It has an internal regulator.
Looks pretty straight forward to wire Old B to Bat, old E to E, old L to the bottom spade of the T shaped terminal and tach wire to the wire on the side of the new alternator.. Will I need to run a wire from the Top spade of the T shaped terminal to the battery for the voltage sense ?? The old alternator (See pic above) did not have a wire like that, but it might have been internally hooked to the B lead - not sure about that. All help much appreciated and needed too (:>) Also I have no idea what the 2 wires that were hooked to the L terminal on the old one went to, but figure if I hook them up to L again should be ok. All thoughts on that appreciated too !!
Currently we (boat & me) are in Mexico in a small port and no local expert help available so the help you folks give me is so needed, waiting 2 weeks for amazon to get the alternator here and sure don't want to hook it up wrong.
Thanks again to all. [IMG]www.cruisersforum.com/gallery/showimage.php?i=13843&c=503][/url][/IMG]
Some how I got mixed up following this regarding the L connection. I suggest that you trace these two wires back and find out where they go. That might help you figure out where to put them on the new alternator. No sense taking a guess and frying the new one.

Where in Mexico are you?
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Old 21-08-2019, 19:28   #13
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Re: Help needed with alternator replacement on a Yanmar 2gm

Typically the Hitachi stock alternators that Yanmar use have two terminals in the T connector. One is marked L and the other is R.
Consider L = light and R = regulator.

Typically the L wire goes to one side of the Charge lamp and the R wire goes to the other side of the Charge lamp as well as the +ve switched side on the Key Switch.

I.E. the R wire has battery +ve on it when the Key Switch is ON as does one side of the Charge lamp.
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Old 21-08-2019, 21:37   #14
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Re: Help needed with alternator replacement on a Yanmar 2gm

My old Hitachi alt does not have a T terminal. Only the 3 posts and the wire coming out for the tach. You can see it good if you click and expand the pic of it in my first post about this. Thanks
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