Cabin Lights on DC Power = Alarm Mystery

[SerenityTC]

I am the new owner of an '83 Hunter 27. I'm very new to sailboats so please forgive me if I am asking a question with an obvious answer.

On DC power, when I turn on the cabin lights an alarm sounds. At least I am assuming it is an alarm. It only happens when I flip the breaker for the cabin lights. It doesn't happen on any of the other breakers. I tried some google queries and saw a couple posts regarding proper grounding as a possible explanation. I hooked up the batteries (2) according to how the cables were marked (black sharpie) but only 1 was fully charged at the time. The connections on the battery terminals are tight but I have not traced the cables back to their point of origin to see if anything is loose.

Can anyone tell me why an alarm would be sounding and what I can do to fix it? I am off to search for the manual and peruse a copy of Don Casey's chapter on sailboat electronics but thought I would ask here as well.

Thanks in advance for your time and feedback!!

 

[kloudie1]

Welcome to the forum !
Could it be that a previous owner wired the depth sounder to the cabin lights circuit? There may be a depth alarm going off. Many depth sounders have an adjustable alarm that may have gotten set too high and is alarming when the power comes on? Dunno.. Depth sounders were not original equipment and folks wired them in strange ways sometimes..

 

[kito]

edited
Ooops....never mind. Brains a little foggy this morning. You said DC ......not AC.

 

[Benny17441]

Where is the alarm sound coming from? Once you locate the source of the sound and identify the fixture it will be much easier to diagnose.

 

[Calif. Ted]

Do you have an inverter onboard ? With one dead battery switching the lights on could trigger the low voltage alarm on an inverter. Otherwise I can't think of any audible alarms on the DC panel usually, 'course you never know what kind of "improvements" a PO may have done.

 

[SerenityTC]

Thanks for the suggestions. I will head back over to the boat today and see if I can pinpoint where the alarm is coming from and how the depth sounder gets power. I do know the autohelm is wired to the cabin lights so it wouldn't surprise me if other things are on that circuit too.

I also found the name of the original owner of the boat when going through the boat. I suppose, as a last resort, I could contact him. The guy I purchased the boat from only had it 1 year and was the second owner.

Thanks again and I will update this thread as I learn more!

 

[SerenityTC]

I managed to trace the sound of the alarm to the autohelm unit in the cockpit. It is an Autohelm ST4000 that I'm not even sure works yet. In reading the manual, it will sound an 'off course' alarm but I didn't see anything about low voltage........ but that is definitely where the sound is coming from.

My plan for this week will include testing my batteries (no idea how old they are) and checking all my wiring connections.

Thanks for the idea to check the depth meter because that got me focused on the cockpit and was able to pinpoint the sound.

I will post again when I find a definitive answer. Thanks again.

 

[SitkaChum]

The ST4000 will indeed alarm with low battery- I forget the exact voltage but I think it's somewhere around 11.5 or 11.9 volts. If you can, it'd be nice to move it off the cabin lights circuit and on to it's own circuit.

 

[Chief RA]

Disconnect the weak battery and use the good one for test purposes. This will tell you if battery is the problem. Chief

 

[braol]

One of the first things I would do is to test the alternator to make sure that it is producing charge. The second thing I'd do is read Maine Sail's embedded tips (http://forums.hunter.sailboatowners.com/forumdisplay.php?f=135) about rewiring your 1/2/Both/Off switch so that you don't fry your alternator by inadvertently switching to "Off" while the engine is running.
With all this done (as well as getting your batteries tested) you can rest assured that everything is charging nicely and that you won't face a situation (always far from home and in the evening) where you can't start the engine or fire-up your Nav/Anchor lights when you need them most. Personally I'd want to know how old the batteries are and maybe shell out some cash for nice new ones. If there is any question at all about the state of your charging system don't spend valuable dollars on new batteries because in the end you will ruin them.
Keep in mind that in a pinch you can hand crank your engine started as it relies on no electricity at all (diesel). Sometimes I hand crank my engine before I weigh anchor after an overnighter just to save those precious amps and not have to charge for an extra 15 minutes....
Congratulations on the new boat! I will be on Lake Michigan (North of Chicago) starting this July in my Hunter 27. I've been in San Diego and Annapolis, MD before and now I am looking forward to sailing on the Great Lakes. Keep us posted on your sailing adventures when you get the boat on the water!!!
Chris

 

[SerenityTC]

Just a quick update: batteries checked out and alternator is functioning properly. Alarm is still going off but the wiring is pretty suspect at this point. As I have been tracing wiring throughout the boat, I have noticed the previous owner simply twisted the wires together and wrapped a bit of tape around them. I will be spending time this holiday weekend re-wiring everything that was done this way. I also ordered a multi-meter that should arrive today so I can get a better picture of what is going on.

I agree with the idea that the autohelm should not be on the same circuit as the cabin lights. Not sure if I will be able to make that change before the boat goes in the water but has been added to the list of projects.

Despite the odd challenges and being completely new to the world of sailing, I am having fun! I have no problems at all spending hours at the boat yard just tinkering around. Now, if I could just get that motivated to do the yard work??!!??

Have a great holiday weekend!

 

[SerenityTC]

6/14 update: I rewired from the panel to the head unit and the voltage checks out now. However, when I connect the cable that runs to the wheel unit, the alarm kicks in. I haven't had time to really dig into this new development but I'm guessing perhaps a continuity issue?!?! Also, even though the head unit is getting power, nothing actually displays.

I will continue to play around with this but it isn't a critical issue for the time being. I have the boat in the water and am enjoying the process of learning how to sail.

Will update as I make progress. Thanks.