Faint CW warning buzzer on 3hm35f

[mckendym]

I have a 3hm35f in my Pearson 36-2. I note that the warning buzzer sometimes emits a very faint sound when under way. I checked the obvious components of the cooling system and everything seems fine. If I flick the switch at the panel the buzzer stops and sometimes may start faintly again. The light does not light up. Any thoughts

[MarkJ]

Moisture? Are you copping waves at the time? Had that happen to me. The control get sloshed and the buzzer goes off

[model 10]

Problem with the loose /bad connection idea is the connection is a ground. So if you have a bad connection you would not get a light or a buzzer. You could have a serious green corrosion trail to ground somewhere or it's really getting hot.

[model 10]

The problem with the loose /bad connection idea is, it's the connection for a ground. So if you have a bad connection you would not get a light or a buzzer. You could have a serious green corrosion trail to ground somewhere or it's really getting hot.

[GordMay]

Greetings and welcome aboard the CF, mckendym.

[deblen]

Possible sticky sender? Replace. / Len

[jhulmer]

I had the same problem on a Yanmar 2GM20 on my previous boat. It would chirp very faintly when running but I didn't have any oil pressure or over heating issues, all was normal. I know it worked normal when I sucked a ice bag up the intake and the engine over heated.

unfortunately, I could never source the problem so I just ignored it for 10 years until I sold the boat.

Sorry, not much help on solving the problem but it might ease your mind a little.
Jim

[alctel]

My 2QM20 does that as well when I'm at low revs for an amount of time (like trolling for salmon). It's almost inaudible but the lights stay off

[Elie]

I had the same problem with my Volvo Penta MD22L.I found that the alternator was faulty e.i. : Some diodes where weak and the voltage generated was borderline line at low RPM. I repared the alternator, and this anoying noise went away.

[model 10]

It's a low voltage thing. If you use OHM's law, as the voltage drops, the resistance of the sender goes up and looks like a ground to the instrument panel. The piezo buzzer uses less power than a light bulb so you hear it first.

[Elie]

in fact the alarm is stoped when the potential difference between the two wires that feed the buzzer is null. the generation of voltage from alternator cancels the voltage feed on the other wire comming from the battery. So: in fact you get 12 V on each side of buzzer wires thus 0 volt is the net result. In your case, your alternator do not create enough voltage to cancel the battery voltage. So the buzzer buzz a bit...

[SV Bacchus]

Welcome to CF mckendym!

[thunderhoof]

I agree that the controller is seeing low voltage, whatever the reason. I had a similar noise from my 35F one day when the battery was particularly low. Check the voltage at the input to the controller when under sail vs engine running.

[bradandnatalie]

I have that exact motor and I had that exact problem. Turned out to be a faulty oil sender switch. It would intermittently come on and sometimes only very faintly. Not a huge problem to fix they simply screw off and replacements are easy to come by. Check the wire connection to the top of the sender unit, it may be loose. If not just replace the unit itself.