Ground fault

[benny37]

A big hello to everyone here and thank you for all the help you provide to newbies like myself.
I bought a 2006 Beneteau 373 last year and am in the process of fixing up the electrics. Like most boats of this age the wiring has been modified sometimes well and sometimes... not so.
The bilge pump has a + feed from the 12v breaker panel but the LED doesn't light and the pump doesn't run. The breaker is good as I swopped it out and the problem persists with the new one. The pump works when connected directly to the battery. I tested the voltage on the supply wires to the pump and get positive readings in both !! Red 13v and Black 0.5V. The pump runs if I find another neutral connection (from the fresh water pump). This suggests a ground fault to me.??
My question is should I tap into the water pump neutral (easiest) or run another neutral wire to the panel and what do I do with the old neutral?
Thanks
Dave

[TreblePlink]

Sounds like your "neutral" - I'll call it negative - is open. Unless the wire has been spliced in the middle, or cut, 99% of problems will be at the ends - usually corrosion or bad crimped connectors. With it on, you might vibrate the negatives at their ends to find the bad one, or just re-terminate the ends.

+13 and +.5 (with respect to boat ground) is not unusual, and provides 12.5 dc to the pump - whih is fine.

[GordMay]

Greetings and welcome to the CF, Dave.

[JohnT]

What make and model pump? Does it have an internal or external float switch? Can you see a float switch? An electric bilge pump will have a float switch to switch it on or off, depending on if there is water in the bilge or not. Some of the systems use water sensors with no switch. All these float switches do sometimes pack up. If it has an internal float switch, and you do not want to put water in the bilge, simply remove the unit (they often just clip into a fixed tray) and turn it upside down when the power is on.

Personally, I would never have a bilge pump switched at the DC board, other than an override switch. I would have it permanently connected to the house battery with an in-line fuse. What if you turn your main battery switch "off" and the boat starts taking on water? Bilge pump will not work! It should be able to work irrelevant if the battery switch is on or off.

Let us know the answers to the above questions and maybe we can point you in the right direction to solve your problem.

Oh, when you tested the pump connected directly to the battery, did you have it upside down? If so, it has an internal float switch which will switch on when upside down - turn it the correct way as it is in the mounted position and it will switch off.

John

[_andi_]

Hi, welcome!

If you tap any other ground or hot wire always consider the combined load on the breaker and the cable. Especially with a bilge pump it would be pretty lame if it's running all out and the breaker goes pop...

So yeah, it would be a good opportunity to run a new wire with an inline fuse from the battery.

If possible remove the old cable to reduce further confusion or at least mark it permanently as defunct, it will save you or somebody else headaches in the distant future...

Also maybe study how to measure resistance properly and how to calculate voltage drop, not too difficult but a real asset to judge stuff going on with electrosity...

Cheers, Andi

[benny37]

Thanks everyone for the suggestions.
I hadn't considered that a +0.5V in the neutral (relative to ground) might be normal but of course as you point out it still provided 12.5V to the pump

The comment about the cable ends being more of a problem than the cable itself is well taken and Ill try to clean up the contacts before I do anything drastic.

I don't think removing the wire is practical as its wrapped tightly in a loom and is fairly inaccessible - behind the couch and nav table and up to the breaker panel. This seems to be a perennial problem with boat elections and makes a simple wiring job very difficult. But Ill be sure to mark it as defunct if I can't improve the situation with a clean up of the connections.

Thanks
Dave