Mystery electrical outage help

[midnightbluejay]

Hi all, was hoping to pick some brains on an electrical issue I'm having with my (old, but new to me) sailboat. After motoring for an hour, we plugged a phone into one of the DC outlets and all of the accessories running from the main DC light panel suddenly cut out, along with the blower. Fuses not blown. Plotter, radio, and windless are not on this switch panel and all work fine. The switch for the blower and primer are in the cockpit, not the other panel, and also have no power, but the depth sounder and gauges in the cockpit work fine. Engine started fine. Batteries reading 12.8v and charging from our solar panels. A few hours later after sitting at anchor, it all turned back on and worked fine again, until the same thing happened that evening. This time it all went out suddenly when the water pump started going. The bilge pump also didn't have power (connected directly to the battery) so I don't think it's an issue with the battery selection switch. But the on/off/auto switch for the pump is grouped with the panel of other accessories that went out.

At first glance, battery connections and wires all look ok where I can reach, but I didn't have time to crawl around with a multimeter to test things. That's my next step when I get back to the boat this evening. Any other ideas on what could be happening and what to look for?

[Shanachie]

Check your ground wires.


Most likely, you have a buss that collects all of the 12-volt ground wires. It will be connected to the battery bank and to the central ground, usually a bolt on an inboard engine.


If the ground wires to the failing circuits are loose, the circuits will shut down as soon as you place a load on them. Clean all of the connections and tighten them.

[Island Time O25]

+1 check for the ground issues.

In my own experience 9 out of 10 mystery outages ended up being caused by faulty ground i.e. loose cables, rust, etc.

[midnightbluejay]

That did it! Many thanks.