Change the circuit so that the relay coil is in parallel with the pump, and
the relay coil is in parallel with the upper switch. Any old 12V relay where
the contacts will carry the load of the pump will do.

"Roger Long" wrote in message
...
Here is the electronic version of what you are talking about, a
latching relay.

http://home.maine.rr.com/rlma/Switch.jpg

The lower float switch goes on and nothing happens. When the top
switch goes on, current flows through the relay which closes a contact
that then bypasses the upper float switch. When the upper float
switch goes off, the relay remains on and the pump keeps running.
When the lower float switch goes back off, the circuit is interrupted,
the relay springs back, and the pump stops.

All this needs to work is a relay rugged enough to handle the current
draw of the pump without heating up or contributing too much voltage
drop. If anyone has specs handy for such a unit, I'd appreciate a
model number because I'll build this thing and report on it.

--

Roger Long