A Leak of a Different Kind

Gary Wells

I spent my day trying to round up some stray Milli-amperes and it leads me to ask the group if a couple of anomalies aren't actually wrong.

This all started when the starter battery died back in September. We'd been off Adagio for about 6 weeks but left it in the care of a boat-watcher who started and ran the engine and GenSet for us .. but apparently not often or long enough and the starter eventually quit starting.  I told them to just leave her be, as the house batteries were on shore power and staying charged anyway.

When we returned the first order of business was a new starting battery and some tests to see why it would have given up so easily.  It was perhaps four years old, but there was more to the story. ...

A little current goes a long way. .. My first look into it revealed a 39.5 Milli-amp (.039A) static drain on the starter system.  As we were about to be off-and-on the boat, and on the move, for a few more months I opted for a good quality 1 Amp battery maintainer and it kept things quite healthy until now, when I could get to what I suspected would be quite a project. 
Well, it's not that bad.  I found the culprit in a previously installed secondary bilge pump switch/high-water alarm.

I will be replacing it with a solid-state switch as it's very cool to me to have a high-water alarm and the wiring is in place for a secondary bilge pump. This makes it easy to connect up .. as long as you remember it's a 12 volt line :)

So, removing that switch I got rid of about 38 of the 39.5 leaking thousandths of an amp.  The other one-and-a-half is playing hard to get.

I've isolated it to the GenSet.  But, before I go diving into it full-tilt (I will indeed start studying the schematics tonight) I'm just wondering if a 1.5 Milliamp draw is worth fighting for.  I presume that it should be a dead zero when things are turned off but maybe the GenSet has some volatile memory?  For the record, there are three 12VDC relays outboard on the Generator box. Removing them did nothing, but removing the 25A DC fuse did bring it down to ~nearly~ zero. I'll have to chase where this brown +12v wire goes once it passes the relays and see if there is anything obvious.  Then, there's the tiniest residual leak (.00058A) when the charging wire is connected to the Kubota's alternator. 

Just posting in case someone has had the chance to chase something like this. 


Gary W.

SM #209, "Adagio"


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