For C Series C12 and C14 Irrigation Kits the are from 2019 and earlier
The older version of water level sensors connect inside the control unit direct to the PCB, whereas later L Series models have a waterproof external screw casing that is used to connect the water level sensor.
To change the water level sensor, remove the rear cover from your C Series C12 or C24 taking care not to disconnect the rear cover battery pack from the internal PCB board.
Locate the existing water level sensor and follow it to the board and unplug.
Remove the sensor from the housing.
Take the replacement sensor and install into the housing and connect to the pcb.
Replace the rear cover taking care not to dislodge and wires or trap the battery cable.
Screw the rear cover to secure it.