Originally Posted by rebel heart
Put a multimeter to the wires at the sump and see if there's any current going across when the switch is on. Current = something wrong with the sump, no current = something's wrong with the wiring
/ distribution between wherever the multimeter is and the batteries.
Methinks you arre thinking a multimeter set on vdc 15 across the terrminals and checking for voltage.
@OP - my sympathies. I recently had to troubleshoot a dead 12v outlet in the pilothouse of a 50 footer. Upside down, tracing and pulling wires. They disappear into a bulkhead to reappear on the other side six inches lower bundled with six other wires. Pretty sure this is these two. Ah, cut these tie wraps, meter the junction. Damn! 12v here. Must have an open wire in the bulkhead. Run new wire, fish
around with a rod, cant find a way through. Never mind lets go at it to tomorrow. We need to start pulling wall panelling and get a drill if we have to.
says, "What about this switch on the panel?" the panel has probably 40 switches. Not all are on. This is not marked and is off and new owner has never turned it on. Switch it on. Voila! Power at the socket! Owner says previous owner said he pretty much leaves the dc panel alone no need to switch stuff all the time. All the other 12vdc works, why is this on a separate circuit? Who knows...
One by one we activate every switch. Lots of switches don't do what they are labelled to do. Some don't appear to do much. A couple of others with fallen labels are id'd.
Inheriting someone else's ideas of "improvements" can be frustrating and time consuming...