Doh! We have a negative switch and didn't think of it. Glad that was it. Our switches in the aft berth and I am always worried about guests staying there might kick one.
Here is a somewhat related story.
We always shut off the negative and both
battery banks when we get off the boat. We usually just start from the house bank, though once a month we start with the start battery. Due to some miscommunication when we boarded the boat for the weekend, I tried to start the
engine with the house battery switch was on but the negative switch off. I turned the key to on, and the blower and
alarm started fine. I turned the key to start and everything went quite. Next time I tried turning just to on, nothing happened. I pretty quickly noticed that the negative was off. I turned the negative on, along with the house, and the boat started normally. We tested a start with the start battery and that was fine too. Though it felt like we blew a fuse nothing seemed to be amiss, so we continued on.
Later that day we noticed that the
bilge pump LED on the DC panel was not glowing as brightly as the others. Eventually we found that a fuse on the negative lead for the always on
bilge pump wiring, that bypasses the battery switches, had blown. The starter had tried to start through that wire. Obviously a damn good thing that both the pos and neg were fused.
I'm not certain what is wrong but the fuse blown, the
bilge pump must have been getting a ground back through something else. Without the negative switched on, the key should not have responded at all. I still have some more investigating to do, then decide what to do about it.
Regarding the problem of shutting off the positive switch with the engine running. Blue Sea has a battery switch with a built in field disconnect.
https://www.bluesea.com/products/900...witch_with_AFD In the event that the battery switch goes to off, the field disconnect stops the alternator from generating electricity and protects the diode. I thought that I saw Blue Sea offering an AFD device to locate near the alternator without having to change the switch to get the same result, but I'm not seeing it on their webpage, which is too bad. I had hoped to install one as part of a
winter project.
Harry
s/v Juno
juno423.blogspot.com