Yanmar GM30F - Alternator wiring

Slycat

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Hi all, I recently had some rewiring done and it feels like the alternator is not doing anything now, despite being driven fine.

Had some difficulty working out which of the connectons are what on the alternator itself, does anyone happen to know?

Its sitting at 12.5 v either when the engine is running or not, I'd swear it was sitting at nearly 14v or more when it was runnnig before!

Thanks,
Chris
 

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VicS

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It certainly wont be charging the battery at 12.5 volts. You are just seeing battery volts, it's not generating Id expect 14 to 14.4 volts.

Check the wiring against the schematic in the owners manual in particular the blue/black wire on the L terminal which is the warning light connection, and the red/black black wire on the R terminal which is the excitation supply from the ignition switch.

How does the warning light behave? Does it come on initially but go out once the engine has been started ?
 

Slycat

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Thanks for this, very helpful!!
I used the warning light as you suggested to diagnose and eventually figured the 'excitation' supply was loose. All working now with 14v across the bats.
Cheers!
 

VicS

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Thanks for this, very helpful!!
I used the warning light as you suggested to diagnose and eventually figured the 'excitation' supply was loose. All working now with 14v across the bats.
Cheers!
Thanks for the feed back.
.
 

B.A.

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Hi I'm in somewhat of the same boat no pun intended. I misread my schematic and thought that my oil pressure sensor was my tachometer sensor. The tachometer sensor on my 3gm30f seems to run to the back of my alternator. I'm not getting any charging out of my alternator and everything on the internet suggests that the oil pressure sensor regulates the alternator. Is it possible that the tachometer would have the same effect. That is turn on the alternator?
 

VicS

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Hi I'm in somewhat of the same boat no pun intended. I misread my schematic and thought that my oil pressure sensor was my tachometer sensor. The tachometer sensor on my 3gm30f seems to run to the back of my alternator. I'm not getting any charging out of my alternator and everything on the internet suggests that the oil pressure sensor regulates the alternator. Is it possible that the tachometer would have the same effect. That is turn on the alternator?
All the information I have indicates that the tacho has a sensor mounted on the flywheel housing looking at the ring gear teeth


1715718468391.png

You should be able to identify the various sensors from the colour coding of the wiring and referring to the wiring diagram in your owners manual.

There is no suggestion that the low oil pressure sensor controls the alternator

Either of these could have been altered by a previous owner.

.
 
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