Wouldn't that be how the pump motor is grounded since the hull should not be.

 

Pump has a black wire - it gets its neg/ground there.

But why the switch?

 

Just to clarify here...

Motor has 2 wires....simple: +12VDC and a Ground/neg terminal. Standard DC motor stuff here...

But the Float Switch has 3 wires: (1) +12VDC in (2) Switched 12V out (3) Ground
Why does a simple magnetic switch need 3 wires?

No where in their documentation can I see any explanation for what the ground on the switch is for.

-J

 

ok...so the engineer in me had to just split this case open to see what is inside this float switch to require both a +12V feed and a negative.

Now, it makes complete sense ...they have a relay inside the switch enclosure!!!! The mag switch they use can NOT handle the 15Amp rated load of the float switch....so they use a mag switch to drive the relay which in turn supports the 15Amp rated load of the float switch. There is a diode (snubber) to deal with any stored energy in the relay coil to dissipate that when the switch turns off.


So, the negative wire to the switch is needed to drive that relay

Some things to note here, the float switch is not water tight. Yes there is a seal around the wires, but water can still work its way into the housing. If that happens, you may get corrosion and damage to the connections around the relay --- which is what happened to me (see picture). I imagine the relay got water (salt) in it too, because when I try to drive this directly with a power supply on the work bench...the relay doesn't work.


Of all the Googling, I was never able to find out what was inside of this float switch to require a 3rd wire (negative). Now I hope this helps the next person seeking the answer