Check that the cable is intact and properly connected to a 12V power supply (red/blue positive, black/negative). Also check that the fuse is plugged and intact.
Access the F2 function and adjust the Monitor volume.
During work, check that all sensors are working, if you identify the absence of one, it may be the lack of battery.
If the monitor is turned off and on again, this sensor will not appear when the F1 function is activated.
Access the F3 function and change the brightness of the screen.
The problem may be communication signal or the antenna may not be properly mounted on the monitor. Check that it is mounted and upright, and try to remove obstacles between the antenna and the sensors. If you have a radio source near the sensors, turn it off.
If the maneuvering state occurs during the shooting of the planting, or if the monitor is whistling, it may be that the fertilizer is leaning against the walls of the sensors. If this occurs, wipe the crusted surface with a soft sponge or cloth, remembering that pressurized water can damage the sensor.
The sensor has high resistance in high temperatures and rain.