Hello Paul and Bill,
Did the splice suggested by Bill work? I have a similar-looking pump, a Jabsco Sensor-Max variable speed control with a solid state pressure sensor. People installed these pumps to be able to remove the water pressure accumulator; our boat has had this pump since August 2012 or before and I made sure to buy a spare before these were discontinued in 2015.
Anyway, I have the same "one wire too many" issue and have been afraid of splicing into the wire going from the Jabsco switch to the Jabsco motor... I figure the sensor probably sends either a pulsed signal or variable voltage to the motor, as it does, in fact, run at different speeds depending on the number of water taps open or how much you open them, and I am not sure what either of those cases would do to the little light on the 24V panel... maybe someone else has tried this before?
SM2K n. 350 (2002)
At anchor, Ajaccio (Corsica)