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Old 22-07-2019, 18:02   #1
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Yanmar 4JH45 "Alt Error" Fuse keeps blowing

On my starboard Yanmar engine I recently got a continuous alarm and the displayed error "Alt Error".

Sure enough, the Balmar 120A alternator is not charging the system. No measured output from the alternator. It is spinning and the belt looks fine, etc. No voltage on the field pin.

I (eventually!) found a blown 5A fuse on the engine fuse compartment. When replacing the fuse, not only did the alternator begin working fine, but the blower fan also came on when power is applied. I hadn't noticed the stbd fan wasn't blowing.

I was surprised to discover the compartment fan was running on the same circuit as the alternator. I assume this fuse feeds to field circuit, obviously 5A is not near enough for the output of the alternator itself.

But now the fuse keeps blowing. Not right away, but after a day or so.

I'm starting to guess the alternator is fine, and maybe the ventilation fan is somehow drawing more current than it should.

Any suggestions or experience?
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Old 24-06-2021, 14:18   #2
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Re: Yanmar 4JH45 "Alt Error" Fuse keeps blowing

Quote:
Originally Posted by Whomda View Post
On my starboard Yanmar engine I recently got a continuous alarm and the displayed error "Alt Error".

Sure enough, the Balmar 120A alternator is not charging the system. No measured output from the alternator. It is spinning and the belt looks fine, etc. No voltage on the field pin.

I (eventually!) found a blown 5A fuse on the engine fuse compartment. When replacing the fuse, not only did the alternator begin working fine, but the blower fan also came on when power is applied. I hadn't noticed the stbd fan wasn't blowing.

I was surprised to discover the compartment fan was running on the same circuit as the alternator. I assume this fuse feeds to field circuit, obviously 5A is not near enough for the output of the alternator itself.

But now the fuse keeps blowing. Not right away, but after a day or so.

I'm starting to guess the alternator is fine, and maybe the ventilation fan is somehow drawing more current than it should.

Any suggestions or experience?
Did you fix this? I am having a similar issue except that my alt seems to be spitting out 5 volts rather than 13 but I have had issues with the fan in the past and wonder if it's related. My alt warning goes on regularly on the Yanmar pannel. BTW, mine is only 2 years old.
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Old 24-06-2021, 14:44   #3
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Re: Yanmar 4JH45 "Alt Error" Fuse keeps blowing

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Originally Posted by SVSweetestThing View Post
Did you fix this? I am having a similar issue except that my alt seems to be spitting out 5 volts rather than 13 but I have had issues with the fan in the past and wonder if it's related. My alt warning goes on regularly on the Yanmar pannel. BTW, mine is only 2 years old.
I think I replied to you on your facebook thread: After thoroughly cleaning all connections to the fan, and slightly increasing the fuse size to 7.5A, the problem seems to have disappeared.
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