Yanmar Battery Low Charge Indicator - Advice Needed

[AliOops]

Greetings,

I am looking for some advice, I have a new (less than 2 years old) Yanmar 3YM 30AE engine with a B20 type cockpit control panel. We are having an intermittent issue with the Low Charge Indicator battery light and buzzer alarm which goes off when starting the engine. When the alarm sounds, the batteries are not charging. Normally if I stop and restart the engine, all is back to normal. The other day however, the alarm would not stop and consequently no charging. We were only travelling from fuel dock to slip so this was not an issue.

We have now tightened the alternator belt (on the standard Yanmar alternator 128990-77310R and A377936C) and checked the connections to the starting battery (all were good). Started fine yesterday. However today on first start the alarm goes and no changing, second start all is fine.

All our batteries (MasterVolt 4x90amp Domestic and one 90 amp engine starting) are 18 months old. The starting and domestic batteries are isolated and only combined after engine is started.

We are in Southern Italy and language difficulties make it difficult to explain this intermittent issue to a mechanic. Anything you could advise me to look for would be very helpful.

Thanks

David

[smac999]

Next time you start it. And the alarm comes on. Rev it up. And see if it goes away. Alts do very little at idle. And sometimes Don’t charge at all.

Do you have solar or wind also charging?

Are you sure the alt is not charging? Or just assuming because the buzzing is on?

[NYSail]

Check your negative connections. Not just tighten, remove, clean and reattach. Also do you have a battery monitor??? If so watch it next time or use you multimeter and check current at back of alt. The alt does not immediately start charging when you start and you will hear the warning for a moment, however should turn off after a few seconds. Regarding language barrier, why not just video starting the engine and show it to mechanic.

Greg

[AliOops]

***Thank you for your assistance, my responses are below at the ****

QUOTE:Next time you start it. And the alarm comes on. Rev it up. And see if it goes away. Alts do very little at idle. And sometimes Don’t charge at all.

*****We ran the engine at various revs on the trip from the fuel dock and the alarm did not stop.

QUOTE: Do you have solar or wind also charging?

*****Yes we also have solar charging it dumps the excess charge through a flexcharge controller and mercury diverts when the engine is running

Quote: Are you sure the alt is not charging? Or just assuming because the buzzing is on?

*****Both our analog blue sea and digital battery monitors showed no charge when alarm was going off (no increase in voltage) and increase when no alarm and charging.


Thanks

[Mike Banks]

It sounds to me like the starter motor key switch on your panel needs checking. One of the things it does when you turn the engine to "Start" is to excite the alternator windings. Once the engine is running, the alternator is self-sustaining.

See if any wires are loose in the switch connections or any of the contacts are not making a connection. The fact that sometimes the alternator works fine is because occasionally they do self-start.

If nothing is amiss as far as the switch is concerned, the next thing I would be testing is the voltage regulator. That means taking the alternator to an auto-electrician. It is a Hitachi alternator, so most of them will have spares.

[smac999]

disconnect the solar and see if it happens again. or add a bunch of DC loads and see if the alarm shuts off as you add loads.

when a battery is already full (if you just left the dock). and other charge sources are present like solar. alternators can turn themselves off. which can alarm. though more and issue with external regulators which you probably don't have on a stock engine

[MarkusK]

Do you have a 1/BOTH/2/OFF Switch? You may have blown a diode in the alt.

[a64pilot]

Originally Posted by Mike Banks

It sounds to me like the starter motor key switch on your panel needs checking. One of the things it does when you turn the engine to "Start" is to excite the alternator windings. Once the engine is running, the alternator is self-sustaining.

See if any wires are loose in the switch connections or any of the contacts are not making a connection. The fact that sometimes the alternator works fine is because occasionally they do self-start.

If nothing is amiss as far as the switch is concerned, the next thing I would be testing is the voltage regulator. That means taking the alternator to an auto-electrician. It is a Hitachi alternator, so most of them will have spares.

I’m going with this and not bad diodes, bad diodes are not intermittent.

If you have a multimeter, the next time it’s not charging, measure the field voltage, then turn it off and back on, if you get voltage, it’s probably the switch.
Plus next time it’s not charging, don’t shut down, just try turning the switch on and off.

I believe field voltage is supplied through the switch if I’m not mistaken