Bilge Pump Wiring Puzzle

[Chief150]

Just got the boat last week...2004 2400SD. Already searched and found previous posts but unfortunately need more help.

The bilge pump worked with the panel switch but not with the float switch. I pulled the pump and float out, disassembled and cleaned them, and bench-tested both according to the manufacturer's diagram. All good now...or so I thought.

In the boat it's a different story. Instead of the black, brown and brown/red wires that I'm supposed to have according to another post, I have the brown/red wire from the panel switch (as it should be). I have another brown wire that is testing as a ground, and two yellow wires that don't appear to be either.

Thinking someone had spliced the yellow in at some time in the past, I traced all four back to the transom where they disappear into the harness and appear to be factory.

Any help would be appreciated.

[mmwjr]

Yellow is the new negative that was adopted since people were confusing it with AC black which is 110VAC hot. I’d be concerned that the brown is showing as negative. BTY there really isn’t a ground on a boat as this is a reference to rather earth or chassis of which neither exist on a boat.

[Chief150]

Originally Posted by mmwjr

Yellow is the new negative that was adopted since people were confusing it with AC black which is 110VAC hot. I’d be concerned that the brown is showing as negative. BTY there really isn’t a ground on a boat as this is a reference to rather earth or chassis of which neither exist on a boat.

Yeah, I'm concerned that the brown is supposed to be a positive but has grounded out somewhere, which may be why the auto float pump didn't run.
I also forgot to mention that the hourmeter runs when the panel switch is flipped for the bilge pump. I need to know engine hours, not manual bilge pump hours!

I noticed that there were several yellow wires coming off the negative post of the battery, and that they are fused. I also replaced the battery charger and noticed that both of those leads are fused. I've long been familiar with 12 volt automotive systems, but I guess I'll have to get used to a new way of thinking.

Thanks for the reply...

[mmwjr]

Interesting that you have fuses on the negative wires, fuses should only be on the positive supply wires.

[Chief150]

Originally Posted by mmwjr

Interesting that you have fuses on the negative wires, fuses should only be on the positive supply wires.

Yeah, that was a new one on me. The hourmeter was connected to the manual bilge pump wire with a tap, so I removed it...should be fairly easy to find a wire that's only powered up when the engine is running.

I ran a new fused positive to the float switch and a new negative to the pump. Done with it for tonight, should be an easy wrap up tomorrow morning.

Thanks again for your comments!

[shrew]

The PO was an idiot who didn't understand electrical of any kind (AC or DC).