Robot lawnmower displays E13 Rain Sensor Error; mower refuses to start even in dry weather or ignores rain.

Safety first: Turn OFF the mower before cleaning or opening the sensor housing.

• Locate rain sensor: On NAC models with rain detection, the sensor is usually on the top cover in a small recessed area.
• Clean sensor: Wipe the sensor surface with a soft, damp cloth to remove dust, pollen, or dried residue. Dry thoroughly.
• Check settings: In the mower menu, verify that the rain sensor function is enabled and configured correctly.
• Inspect wiring: Remove the top cover and trace the rain sensor cable to the main board. Ensure the connector is secure and free of corrosion.
• Test behavior: Simulate rain by lightly moistening the sensor (if allowed by NAC manual) and observing if the mower responds. If there is no change or constant E13, replace the rain sensor module.

Warning: Do not pour water directly into the mower housing. Avoid harsh chemicals on the sensor surface.