Lagoon shower sump turns on but not off

[StarfishEntrprs]

Utterly. Baffled. Bought a 2008 Lagoon 420 recently. When the float switch in the shower sump goes up, the pump comes on. After the float switch drops, the pump doesn't turn off. I've waited over 60 seconds for it to turn off (using a watch), and it never does. I don't know if the problem is new, unfortunately.

Pump has been connected to power directly and works fine. It's a Whale Gulper pump. The manual on/off switch on the control box works fine and cycles the pump on and off manually as expected (it's a Scheiber control box https://store.marinebeam.com/scheibe...ay-with-delay/). The pump also pumps properly at a rate that seems right to me. Voltage at the control box matches the boat's battery monitor (about 13.5V). Pump draws about 1.5A when on, which seems about right. Finally, I've tested the float switch repeatedly, and on an Ohms setting my multimeter says OL (open circuit) when the float is down and 0 ohms when the float is up. The float switch seems to work properly over repeated cycling, both using water and manually.

Once the float kicks the pump on, it stays on indefinitely until I manually disconnect the float switch from the control box. Then it will turn off after the few second delay.

The real kicker is that I found a spare control box, new, in the old owner's stash. I tried it as a replacement for this control box, and it behaves identically.

The other shower on the boat works fine and turns off after the short delay after the float drops. I measured ohms on that float switch, and it behaves the same as the one on the shower that's not behaving. Finally, I plugged all the connections from the working shower to the spare control box, and everything worked fine. So in both the working shower and the non-working shower, swapping control boxes doesn't change what is or isn't working.

As far as I can tell, replacing the float switch is a big operation since it's inaccessible without ripping out all the caulk around the shower sump and then recaulking it. So I'm trying to avoid that unless I'm confident it's the problem.

I would be hugely appreciative of some help!

[tkeithlu]

It sounds as though the float switch is sticking in the up position when it is floated up. Float switches are evil-minded devices that take great pleasure in doing this. Pull the switch, clean its pivot and any gunk or trash near it, reinstall. It's a very common event, unfortunately.

[chrisr]

[SVNeko]

It's the float switch. If you plan on keeping that boat for a while, better plan on making it accessible. It's a wear item.

[a64pilot]

Replace the cheap float switch with a good one.
I’ve had very good luck with these, mine are the jr model.
https://www.ultratef-gel.com/ultra-pump-switches/

[OldGreyB]

Your description stating that removal of the float switch wires causes the pump to stop after a few seconds is indicative that the control box and circuit are correct, and the opening of the contacts to the control box cause the correct response.

So you have proved to yourself, and as others have stated its the float switch contacts are sticking, however your own multimeter measurements of Open Circuit and Closed Circuit indicate that is not happening, which is where your confusion is why the circuit is behaving like it is.

You have not stated if the float switch and control box are closely connected, or via long run of cabling, but assuming it has no other suspect connectors in the circuit, then probably what is happening is while the multimeter measurements of Open Circuit and Closed Circuit as reported seem correct with float movement, with the small control current supplied when the control box is connected, the float switch appears to be passing sufficient current leakage (via salt air junk around the float switch contacts) to allow the control box circuit to remain energised. You can prove this by putting your multimeter into milliamp reading and in series with the float switch and measure the milliamps as the float switch changes from open to close. If it's as described, you will not see much of change, and the pump will continue to run. OR the internal resistance of the meter will be sufficient that the control box will sense an open circuit and the pump will stop. As all the other posters have stated, marine float switches are typically cheaply made, evil minded devices.

Additionally to fully validate the error is in the float switch: Connect a short piece of wire instead of the float switch on one connection at the control box, and then replicate opening and closing the float action with the short piece of wire to the other connection on the control box. We expect the pump to run when both wires end are connected, and then stop after the control box time delay when one wire end is disconnected. If neither of the above resultants happen then, post back.

Otherwise follow other poster's advice and remove and clean / replace the float switch. Follow a64pilot's sound advice and only buy good quality float switches and mount so they are readily serviceable.

The shower float switches are least of your worries, since the boat is new to you, you need to ensure your bilge ones work every time and you have a good spare on board for those.

[chris95040]

Note that float switches -deactivate- at a different height than where they -activated-. This is to prevent rapid on/off cycling at a particular water level.

This phenomenon confuses a lot of folks when they first see it but it’s absolutely essential.

These numbers are just made up, but a small bilge float switch will typically activate at something like a 3” relative water height and won’t deactivate until something like a 1” relative water height.

Most folk’s first intuition is that the switch is activated at a certain height, say 3”, and deactivated any time the water level is below that. But imagine how that would behave in real life, as water ripples and the height rapidly bounces between 2.9999” and 3.0001” and your pump cycles on and off a hundred times in a minute.

Having separate activation and deactivation thresholds is how control system engineers solve this, and this solution is known as ‘hysteresis’.

The thermostat in your home is another example of this. You don’t want your boiler firing on and off rapidly when the room temp is hovering around 68 degrees F. So it activates the boiler at, say, 67F, and deactivates it at, say, 69F.

[wrwakefield]

Since the float switch is in a shower sump, have you checked for muck underneath it that may be preventing it from gravity falling all the way to switch-off point? [Ask me how I know...]

I finally became fed-up with mucking out shower sumps, and fixing/replacing the float valves. I replaced both sumps on our boat with Whale IC pumps.

We use our onboard showers year around [full time liveaboards] and these Whale IC pumps have performed flawlessly for 3+ years now without any maintenance other than occationally tossing some enzyme [e.g., CP- which also eats soap scum- or Marine DigestIt] down the drain to 'sweeten' it...

They have built-in delay on and off, so it doesn't short cycle, and clears the line after water flow ends... This would eliminate your sump and already has the functions of your Scheiber control box built-in, so you could recycle it to put a time delay on your maintenance bilge pump if needed... Your Gulper pump can also be repurposed...

In case you also become fed-up playng with your slime collection boxes...

Cheers! Bill

[StarfishEntrprs]

Thanks all! I replaced the float switch and everything works right as rain. Special thanks to OldGreyB for explaining why testing the float switch seemed to show that it was working fine (manual cycling, checking with multimeter, etc.) even though it wasn't... that was what was driving me nuts.

I put back in a new OEM float switch which honestly seems like an OK design from the look of it. I'll see how long it lasts, and if not long, I'll look at those other companies mentioned.

[tkeithlu]

A bilge pump with an internal float switch, inside the grating at the bottom of the pump, might last longer, but on the other hand, plan on regularly removing hair from whatever float switch you use, given that it's a shower.