Wiring for shower sump sensor switch

I have to replace the electric field sensor switch in the shower/galley sump. The old one is an electric field sensor switch like in the upper left corner in the attached wiring scheme. I want to replace it with a simple float switch like the one in the upper right picture.
I am pretty helpless when it comes to wiring the electrical stuff. What I don’t understand is this: The old switch has three wires, while all the replacements I can find have two. I have attached a wiring scheme as it is by today.
Could somebody who knows this stuff point me in the right direction of what goes where?
Thanks in advance!
Walter

 

The old sensor is electronic, so it needs a power feed to work. The mechanical switch doesn't. Just cap off the red power wire and preferably disconnect the power to it.

 

Yah..what gonzo says sounds correct. The new float is a mechanical switch.... when its arm floats up it completes the circuit and turns on the pump. Only two wires needed.

The old unit was a sensor that triggered an electrically operated relay inside the unit and this relay completed the circuit and turned on the pump . Three wires are needed.

Eliminating the third wire , red that powered the relay , sounds correct. A multi meter will tell you

 

The two wired coming out of the fuse box Red and Black look like the positive and the negative, they have put a fuse on the negative side as well.

The original sensor has a signal voltage (Brown) that went to your pump and the from there returned to the negative side by joining to the black.

As you are now using just a switch, you need the Red wire (Positive) to connect to the switch. From the switch you connect to the pump and the pump is then connected to negative via the Black wire.

The pump should be connected the correct way and be labelled Positive and negative.

Poida

 

Float switches have a brown with a white or yellow tracer for the power supply.

 

Thank you all for your help! Will get to it next weekend.
Walter