[C320-list] Strange "thunk" electrical noise

[Dann Daggett]

You might also check the compressor.
Dann

-----Original Message-----
From: c320-list-bounces at catalina320.com
[mailto:c320-list-bounces at catalina320.com] On Behalf Of Bill Culbertson
Sent: Thursday, December 27, 2007 4:53 PM
To: C320-List
Subject: [C320-list] Strange "thunk" electrical noise

I finally made the drive down to the marina yesterday to check on
Harmony.
We'd had a big rain a week back which melted all of the snow and
yesterday
was about 40dF and sunny so it was quite pleasant.  All was well aboard
and
it was comfy under her winter cover.  The batteries didn't need as much
charging as they usually do.

Then as I was closing up shop I shut off the main battery switch and
remembered something so turned it back on.  There was a distinct "thunk"
sound.  Strange.  I repeated off, on and each time there was a thunk.
Location was ambigous but seemed starboard about deck height.  I have a
Link20 monitor so after I turned off all cabin lights and everything
else
electrical, I could confirm that there was nothing drawing any current.
In
that state, I could switch it off and on without the thunk.  But turn on
one
cabin light and repeat and "thunk".  Again via Link20 I confirmed that
only
one cabin light's worth of curren was flowing when I turned the switch
on
and heard the thunk.  To be certain, I toggled the windless breaker by
the
battery switch (Harmony is #859 and has the switch on the starboard
panel)
to be certain it was disengaged.  

I also pulled the starboard cushions and boards to better localize the
sound
and to inspect everything in that area.  The sound is not from the
settee
area and I saw nothing unusual down there.

This baffles me and worries me.  I didn't smell anything.  I stuck
around
for quite a while after disengaging everything to see if there was any
electrical smell or anything to raise more fire worry.  

Anyone have ideas?

 -bill