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Bruce in Bangkok[_8_]

In article ,
says...
About 10 minutes after departing from my first anchorage under power, there
was a shrieking sound like a slipping alternator belt or bad bearing from
the engine area. I shut right down and investigated. Belt tension was
proper, no sign of rubber powder or wear. Started the engine up and it was
fine.

About half an hour later, static like chirping noises began coming from the
engine panel alarm speaker. These were intermittent and in a random
pattern. The best explanation I could come up with was that something was
trying intermittently to send an alarm signal to the panel but wasn't
getting enough power through to light an alarm light or fully engage the
buzzer. At the next anchorage, I rechecked the alternator belt tension and
verified that it wasn't the coolant alarm by disconnecting that sender unit.
I couldn't disconnect the oil pressure sender due to a corroded screw that
will have to wait until I take the oil filter off.

The prime suspect is the charging circuit. Battery voltage makes the alarm
sound and the light go on. The voltage regulator in the alternator sends
voltage through a diode to counteract this current. When they balance, the
light and buzzer are off. If they don't balance, the lights and alarms go
on. It seems therefore, that a slight imbalance occurring intermittently
could cause the annoying chirps in the buzzer. This didn't re-occur during
the remaining 7 days of the cruise but I'm curious if anyone has experience
anything like this or if one of our battery and alternator experts can make
anything of it. The big question is whether this is an early warning of
something going south in the alternator or voltage regulator.

I've had this happen years ago with automobiles. Usually when the
lights, heater, wipers, etc., are all on and the load is nearly what the
generator could put out. I've also had it happen with a modern
alternator when the brushes got extremely worn.

You should have a system volt meter installed (I can't see how you can
live on battery power without one :-). If the alternator is putting out
correctly, and depending on the type of regulator you have, system
voltage should rise to 13.something. If it doesn't then you have either
a bad alternator or a bad regulator.

Of course, you can have a bad connection in the instrument wiring
harness. I had a Yanmar that had some corrosion in the connector where
the wiring harness comes off the engine. used to unplug it and plug it
back in a couple of times to wipe the terminals when things didn't work.

--
Cheers,

Bruce in Bangkok