So we traced the leak back to the bow thruster. Not sure yet what is wong with it. Chances are some carbon dust from the brushes creates the negative-grounding connection.
We built another leak detector with a LED bulb and 2 wires to second the amel detector. We plug one end on the grounding and the other end to the positive of the 24V battery bank. A leak on the negative circuit would light the bulb. We found it's more sensitive than our amel built detector and would show a dim light even when the amel detector wouldn't light (to the naked eye). That may show our amel detector isn't 100% working order. I'll troubleshoot that next.
One aspect of the issue we are still a bit confused about:
Despite disconnecting the big cable that connects the battery bank to the front locker where the bow thruster (and others components like the windlass, etc) are, we would still see a strong leak. We had to disconnect another cable that goes in the engine room to remove the leak altogether. There we thought we had 2 sources of strong leaks....
We failed to trace the ER leak (while forelocker cable disconnected from the battery bank's end), so we concentrated on the forelocker one (while ER cable disconnected). When we eventually disconnected the bow thruster from its end and reconnected everything else from their end in the forelocker, we could see only a very dim leak (and undetected by the amel detector). We then reconnected the ER cable, expecting to see and diagnose the second strong leak, but it was gone...
So is it possible that the ER cable was showing the bow thruster leak despite the main forelocker cable being disconnected?
If yes (and it seems to be the case) then the methodology of disconnecting all-but-one cable from the batteries is somewhat flawed... The ER cable lead was a going roundabout.
On a positive note, we now have a better handle on the cable soup (tidy, but opaque) in the ER. Bring on the labelling machine!
Amel 54 #122
Saint Martin, FWI
We had the same. Comes and goes. Eventually we discovered it was dependent on another boat near us-- it would happen when the other boat docked andhooked up to shore power, then disappear when it left. Months later, in another location it happened again. I have had the feeling we were ending up detecting a leak in a nearby boat (boats at most marinas share the same ground, even use your zincs if they don't have them). I have no idea how this is possible, maybe some of you with more electrical knowlege do! We also have a galvanic isolator with detection as well and no correlation with its indicators. The only time our galvanic isolator showed a leak was in a questionable marina in Greece. Tests with a volt meter showed the galvanic isolator was solving the problem even though indicating a fault. The Amel indicator showed no fault. BTW the addition of a galvanic isolator slowed our rudder zinc loss to near zero.
Bob and Suzanne, KAIMI SM 429 In the water in Malta
PS Adm Bill--should I post my Amel WOB results?