[C320-list] Mystery electrical component

[Gene Helfman]

 On Satori (#398, 1997) there's a small ( 3" x 3"?) blue electrical box in
the shaft area, mounted port side, just ahead of the cooling water valve.
It has 4 wires leading into it.  Three wires plug in together like the
lighting attachment on a boat trailer (blue, white, black i think) and the
third is separate, connecting via a blade on the left.  There are three
small lights in a vertical row that are green, green, yellow from bottom to
top.  When I turn on the house battery, the lower green light illuminates.
When the engine is running, both green lights glow.  I don't remember when
the yellow light lights.

What is this box and what is it telling me?  Should it light up when I'm
plugged into shore power with batteries off?

thanks
-- 
Gene Helfman, Professor Emeritus
Odum School of Ecology, University of Georgia
PERMANENT address:
    498 Shoreland Dr., Lopez Is., WA 98261
    (360) 468-2136
    genehelfman at gmail.com

*I'm a mad scientist.  And I'm growing madder with each passing day.*