If the bilge
pumps are controlled by a switch that has OFF, ON (or MANUAL) and AUTOMATIC positions then all these units I am familiar with have only one power connection to the battery, the line with the fuse in it. The other wires go to ground or the automatic float switch.
If the switch is set on manual or on, then it sends power directly to the bilge pump
. If set to automatic then power is sent first to the float switch and then IF the float switch (or you might have an electronic sensor, optical or other type of automatic switch) sees water
THEN power goes to the pump
So, first activate the water
switch (float or whatever kind you have) and see if the pump comes on. If you have a meter and know how to use it, check to see if 12V power is going to the float switch when the system is switched to automatic.