Adding a bilge pump float switch

[sanibel sailor]

I just bought a Cape Dory 24 trawler. Electric system is very simple. There is no bilge pump float switch, only a circuit breaker (with a light) and a switch on the dash also with its own light. There is a third bilge pump wire already run to the dash area. The dash is nicely varnished wood and I don’t want to drill more holes in it to install an additional switch. Pump is a little 800 gph that draws 3.5 amps, which is adequate as the bilge is generally dry. There is a hood manual bilge pump also. And the boat ha positive foam flotation.
My goals are to add a float switch with an alarm that will go off when the pump activates on auto (but not on manual) and to have the existing dash light go on when either pump runs on either manual or auto.

I think I can accomplish this by adding an in-line relay between the hot side of the existing dash switch and the float switch. The switching circuit should be able to handle the <4A current for the pump.

Will my wiring diagram work? I cannot think of any way to simplify it. Suggestions welcome but I don’t want to drill more holes.

[wyb2]

You seem to have 12v on both sides of the alarm when the float switch is closed.

It’s been a long time, but I think I used one of these two-way switches. Manual position is wired straight to the pump. Auto is wired to the float switch with the pump and buzzer (not included) in parallel. No relays. I think the auto light is always on when in auto though. You could add another in parallel with the pump and buzzer.

I doubt I put the breaker on the negative like they show. For Amazon products, I consider the wiring diagrams to be loose suggestions.

https://a.co/d/dWDszFC

[toddster8]

There are already three wires running to the pump? Are you sure it's not one of those with an internal water sensor? They take a little sip every x minutes and if they detect resistance, they keep pumping. No float switch involved. They have a third wire for manual operation.

If not, serving suggestion: No spliced connections in the bilge - run all wires to a high and dry terminal strip above somewhere. Will help with trouble-shooting and replacing components in the future.

[wholybee]

No, that diagram will not work. You have the alarm in series with the pump, which will not work.

[wholybee]

Here is how it could work.

First, I connect the float switch via a fuse to the battery, not to the breaker panel. This ensures it will still work if I am not on the boat and all the breakers are off. But if you like you could connect to the breaker instead.

The float switch activates the buzzer, and the relay. The relay closes and activates the pump and illuminates Lamp 2.

[wholybee]

On my boat, I have a "high water" alarm that is a completely separate circuit, and a few inches higher than the pump, so it only alarms if there is a problem, not for maintenance pumping. So I don't need a relay. But instead, I have a counter connected to the pump, so I know how many minutes it has run. It doesn't matter if manual or auto, if the pump is running, the meter counts. That way when I get to the boat I know if the pump has run and how long.

[sanibel sailor]

Originally Posted by toddster8

There are already three wires running to the pump? Are you sure it's not one of those with an internal water sensor? They take a little sip every x minutes and if they detect resistance, they keep pumping. No float switch involved. They have a third wire for manual operation.

If not, serving suggestion: No spliced connections in the bilge - run all wires to a high and dry terminal strip above somewhere. Will help with trouble-shooting and replacing components in the future.

Two wire pump. There is a wire running from dash to the area near the pump.
I plan on using a terminal strip.

[sanibel sailor]

Originally Posted by wyb2

You seem to have 12v on both sides of the alarm when the float switch is closed.

It’s been a long time, but I think I used one of these two-way switches. Manual position is wired straight to the pump. Auto is wired to the float switch with the pump and buzzer (not included) in parallel. No relays. I think the auto light is always on when in auto though. You could add another in parallel with the pump and buzzer.

I doubt I put the breaker on the negative like they show. For Amazon products, I consider the wiring diagrams to be loose suggestions.

https://a.co/d/dWDszFC

I actually have one of these switches from Rule, but it won't fit where the current switch/light is. This would leave me with new holes and two empty ones to deal with. Their wiring diagram shows the light wired to two grounds.

[sanibel sailor]

Originally Posted by wholybee

On my boat, I have a "high water" alarm that is a completely separate circuit, and a few inches higher than the pump, so it only alarms if there is a problem, not for maintenance pumping. So I don't need a relay. But instead, I have a counter connected to the pump, so I know how many minutes it has run. It doesn't matter if manual or auto, if the pump is running, the meter counts. That way when I get to the boat I know if the pump has run and how long.

I have this alarm setup on my sailboat.

[sanibel sailor]

Originally Posted by wholybee

No, that diagram will not work. You have the alarm in series with the pump, which will not work.

Thanks Warren.
How about if the alarm has its own ground?

[GordMay]

Bilge Pump Wiring Diagrams:
On-Off-Auto ➥ https://www.cruisersforum.com/galler...r&imageuser=79
/w Alarm ➥ https://www.cruisersforum.com/galler...r&imageuser=79

[wholybee]

Originally Posted by sanibel sailor

Thanks Warren.
How about if the alarm has its own ground?

The side of the float switch connected to the pump also need to go to ground to work. Once you do that, your drawing is the same circuit as mine, just drawn differently.