Strange alarm after installing a new battery??

[David in Sandusky]

Arrived at our marina this morning to step our mast with a new Harken furler. Our battery was too low to crank the engine (2nd time on this battery)so I got a starter battery from the marina. Cranked the engine - no problems through the mast stepping process and return to our slip.

Decided to buy a new battery. After tuning the mast, and setting up the boom and main, I installed the new battery, connecting it as always before. We had an immediate low volume ringing alarm sound. Not the one that sounds when I turn the engine key, before engaging the starter. Did start the engine which was normal. Engine noise made it impossible to tell if the ringing/alarm was still there. After shut dowon, it was there.

Tried disconnecting all wires on the battery. (Radio and depth guage are direct connected.) Sound persists with only the two main power connectors. Sound seems to be coming from the starboard cockpit Lazarette behind where the standard Yanmar control panel is installed.

Configuration:
1GM10 Yanmar new around 2012
Single battery for starting and load on the hook.
Depth guage
Horizon Intrepid radio with antenna at top of mast
12 volt outlet for the autopilot, but nothing attached.
No other sensors or alarms that I know of. (We have sailed our boat around 8,000 nm over 24 seasons on Lakes Erie, St. Clair, and Huron.)

Cabin and navigation lights.
110 volt shore power system for lights, charging electronics, and microwave. Not connected to the 12 volt system.

Marina staff has gone home. Pretty sure they won’t be in tomorrow. Don’t know any local marine electricians. No referral from the local West Marine store.

Any ideas for further trouble shooting, or possible sources? On a 47 year old boat with an unknown number of prior owners, there could be stuff we don’t know about on the boat.

Thanks in advance,

David

 

[David in Sandusky]

Planned actions:
Pull control panel while connected to try to identify alarming item.
Observe panel lights after sunset when it is easier to see them.
Checked oil level.
Find a local expert on electric system/engine.
Note: alarms sound when power is turned on, and before ignition key is turned.

 

[Davidasailor26]

Your proposed actions sound as good as any. Narrowing down the source of the sound will be the most important step. If it really is the engine alarm buzzer there may be some kind of a bad connection causing it to be low volume. Strange timing with the battery change though.

 

[David in Sandusky]

Results of dusk light test:
power on - charging and oil lights come on, alarm sounds
turn key - charging light goes off. Oil light on, alarm sounds.
start engine - all lights off, alarm off.
stop engine - both lights on and sound returns
power off - no lights or sound

Thinking we are safe to travel to Kelly’s Island anchorage tomorrow. Can’t see an operating danger from these symptoms…

 

[Davidasailor26]

Results of dusk light test:
power on - charging and oil lights come on, alarm sounds
turn key - charging light goes off. Oil light on, alarm sounds.
start engine - all lights off, alarm off.
stop engine - both lights on and sound returns
power off - no lights or sound

Sounds like how it’s supposed to work.

 

[David in Sandusky]

No, there should be no alarm when I power on. That means switching the battery from off to on for the whole 12 volt system. There should be no electric response of any kind from the engine electric subsystem until the engine switch is turned on.

 

[Davidasailor26]

No, there should be no alarm when I power on. That means switching the battery from off to on for the whole 12 volt system. There should be no electric response of any kind from the engine electric subsystem until the engine switch is turned on.

Ah, you are correct. I was misinterpreting “power on” as “engine key to on, but before trying to start”.

Do you know if the warning lights are incandescent or LED? Looking at the wiring diagram at Yanmar 1GM10 Operation Manual (Page 84 of 92) | ManualsLib I suspect something’s shorted, but it’s hard to figure out what. LED’s will only light if the current is flowing in the right direction so knowing what type of bulb they are might help the troubleshooting.

 

[Davidasailor26]

Also, do you know whether you have the Type A panel or Type B? The differences are shown at Control Equipment; Instrument Panel (Optional) - Yanmar 1GM10 Operation Manual [Page 21]. The wiring diagram for type A is a bit more complex and seems to have more chances for odd things to happen.

 

[kloudie1]

Check the ground wire connections.. in the main harness.. especially where the grounds connect to the harness. That is a longshot but it is quick to check.. The three black wires below the starter motor in the diagram.. Disconnect one from the alternator for an additional check..

 

[David in Sandusky]

The panel is option B.

 

[Davidasailor26]

After some head scratching and looking at the wiring diagrams the one explanation I can find is that the wire from the panel to the L terminal on the alternator has somehow become directly connected to the output of the battery switch. Basically I'm suggesting that the L wire came off the R/L connector and shorted to the battery positive line, the way I've drawn the red line here.

The L terminal is supposed to be used as part of the charge warning light. When the key is on it should only carry current if there is no output from the alternator. My suspicion is that the L wire is connected to the output of the battery switch in such a way that when the key is off current is going "backwards" through the charge lamp, onto the R wire, through the 50 ohm resistor, onto the L wire in the regulator, and through to ground. Since the R wire connects to the "downstream" side of the key switch having voltage there would feed the buzzer and other lights as if the switch were on, so they come on since the oil pressure switch is closed. The resistance of the charge lamp would explain the relative quiteness of the alarm. When you turn the key on there's 12V on both sides of the charge lamp so the light goes out and everything seems normal. Though I bet the lamp wouldn't come on if there really were a charging fault.

I guess the best way to check my suspicion would be to trace the wire from the charge lamp to the L terminal. If the wiring diagram is right that should be a blue/black wire. See if that goes anyplace other than the L terminal on the alternator. You could also check for connectivity between the output of the battery switch and that pole on the charge lamp. It should have either high resistance or no connection at all. If you see low resistance then I think that's your problem.