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Kohler Generator Trouble Shooting Help

190 Views 8 Replies 4 Participants Last post by  Reinier
Hi all,

I'm new to this forum and joined because I have a problem with my diesel Kohler Generator 9EFOZD 9kva on the boat.
It has been starting and running normal for the last 2 months (except for occasional depleted start battery in the beginning but that has been staying charged when I keep the battery isolated completely when the generator is not in use).
Then yesterday it started normal but shut down within 10 seconds with fault code UU, meaning 'Under Voltage'.
I've checked and cleaned 3 fuses that are on the electrical wires. Replaced the fuel filter which did not seem dirty, tensioned the alternator belt. Also did a complete power off reset, but so far no change.
If there is someone here with knowledge of these generators or willing to lend some help remotely, it would be great! I am in Turkey, a somewhat remote location where the local tech support seems to be away for a few days...
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Reflecting on my own post, this might (might also not) be relevant:
The generator has an AUTO start function, which when selected on the generator itself, would normally enable the generator to start from pressing a button on the boat's main electrical panel that is some meters away. However, I noticed that too drains the start battery fast. And in fact, the start fails when using this option, as if not enough power. Funny enough when using the switch on the generator itself, it starts completely normal (but does shut down after 10 seconds with UU fault meaning Under Voltage).
My electrical knowledge is limited but I believe I read somewhere about a capacitor in the generator's electronics, that might be broken, and so drawing too much power, draining the battery if left on when the generator is not running, and also preventing it from being able to use the auto start function...
Post the serial number.
I went here:
No 9 KW shown.
2153475 is the serial..
Will try to look into how to check the brushes and slip rings. Would be new to me but don't mind getting my hands dirty..


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Pull the end cover from the alternator. The brush holder should be easy to access and remove. Mark the wires and brush position so they go back the same way. Once removed you should be able to see the slip ring contact areas. Examples of bad brushes an damaged slip rings.


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Aha! Thanks a lot Flopshot, really appreciate this and will at least give it a go tomorrow !
But I’d also check the condition of the battery…especially if it’s run down a few times. Bet it’s weak. 😬
Update: I got hold of the service manual for the generator, and was able to test the output voltage. It's a 230 volt AC unit so that's the reading I expected. But it reads 10 and occasionally 11 volts, while the generator runs for it's first 10 seconds. I also tested the meter on our inverter output on the boat the same way, that reads 230 volts AC exactly (it's powered by the battery bank and solar).
I tested the generator starter battery and it reads 13 volts (DC) every time. It has no issue starting the generator. But the UU 'under voltage' fault remains which shuts the generator down after 10 seconds..
Just wondering what the reading of 10-11 volts on the output tells me..
I havent been able to access the slip rings or brushes yet.
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