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Old 18-08-2019, 16:51   #16
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

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Originally Posted by gstent View Post
Yes warning lights are off (and never came on apart from usual start up procedure)
4JH5E
Only on one engine - other fine (Lagoon450)

Thanks for the info
OK, I don't have a 4JH5E manual but I do have the 4JH4 manual (along with several other Yanmar manuals). The Yanmar alarm design philosophy / methodology is very similar across their range of small marine engines so I am confident that what I have written below will pertain to your engine. Note, there are some options mentioned that might not be fitted to your installation but nevertheless, the loom includes the provisional wiring for these options and as such, may give rise to a fault symptom.

There are five possible alarm inputs that will trigger the buzzer (and light an idiot lamp).

1. low oil pressure
2. high coolant temperature
3. water in sail drive seal
4. water in fuel filter
5. insufficient raw water flow

If the alarm sounds and there are no lights on, check the bulbs.

You can trouble shoot the alarm system without the engine running simply by turning on the key switch and disconnecting the wire on the low oil pressure switch on the engine. If all is normal, this should stop the low oil pressure alarm form sounding.
If the buzzer remains on, then trouble shoot each of the remaining four circuits (above).

Each one works the same way. There is a sensor for each circuit - find the sensor and disconnect the wire from it. The alarm and it's associated light should be OFF. Now connect the wire temporarily to ground (battery -ve). the buzzer should sound and the light should illuminate.

Keep removing each sensor wire (at the sensor) until the buzzer stops - this is the faulty circuit.

Remember to refit all the removed wires before closing up - especially the low oil pressure one!
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Old 18-08-2019, 17:01   #17
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

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Originally Posted by ColinIOM View Post
........

And NEVER turn of the ignition switch when the engine is running, (unless it is designed with an electric engine stop and specifically tells you in the instructions to do so) it could (and May already have) blown the alternator diodes (which may be the reason the tacho is not working!
Sorry for the bad news.
Colin
Turning off the key switch on a Yanmar panel while the engine is running will not damage the alternator..
It will disable the alarms (lights and buzzer) and stop the alternator from charging but it won't harm the alternator.

You may be getting confused with say disconnecting the main battery switch or other battery switches). Turning these off can damage the alternator but turning the panel key switch off - won't.

The alternator is only damaged when it's output is disconnected while it is under load. The key switch does not disconnect the output of the alternator.

Quote:
Originally Posted by Mike Banks View Post
Your alternator voltage regulator may be kaput, or the brushes on the slip rings in the alternator worn out.

Annoying--but not a biggie--less than a hundred bucks--
This may be the reason the tacho is not working but these items will not cause the buzzer to sound.
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Old 18-08-2019, 17:53   #18
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

I once had a Yanmar buzzer start going off all the time for no reason. Turned out the buzzer itself was bad. Ridiculously expensive in St. Maarten but also maddening as hell. I would second the advice above to clean all the connections on the back of the panel.

SK
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Old 18-08-2019, 18:22   #19
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

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Originally Posted by sck5 View Post
I once had a Yanmar buzzer start going off all the time for no reason. Turned out the buzzer itself was bad. Ridiculously expensive in St. Maarten but also maddening as hell. I would second the advice above to clean all the connections on the back of the panel.

SK
Yes, the OP may simply have a faulty buzzer, while uncommon, it is possible as you experience shows.

There are several versions of the Yanmar buzzer with the principle difference being whether the isolation diodes are internal or external to the buzzer.

I don't know if the OP's 4JH5E has internal or external but I suspect they will be external as that is what is used on the 4JH4 series.

In the OP's case, he can easily check the serviceability of the buzzer itself by substituting it with the buzzer on his other (working) engine panel.

If the circuit is using external isolation diodes, the buzzer can be replaced with any 12V generic buzzer should the OP wish to avoid Yanmar's overpricing parts policy.
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Old 19-08-2019, 00:09   #20
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

no tach + buzzer probably means dead alternator. most boats have a buzzer / light for charging. and some boats have the tach from the alt.
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Old 19-08-2019, 04:18   #21
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

Lagoon 400 Yanmar issue with electric system. - Cruisers & Sailing Forums
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