Robot lawnmower shows E9 and stops; often associated with rain or heavy dew.

Safety first: Turn off the mower and bring it indoors or under cover before opening any panels.

• Dry the mower: Wipe the top cover and rain sensor area with a dry cloth. Allow the mower to sit in a dry, ventilated place for several hours.
• Inspect rain sensor: Locate the rain sensor (often a small PCB with exposed tracks on the top housing). Check for corrosion or dirt bridging the tracks. Clean gently with isopropyl alcohol and a soft brush.
• Check gasket and seals: Inspect the top cover seal and any grommets around the rain sensor cable. Replace damaged seals to prevent water ingress.
• Verify wiring: Ensure the rain sensor connector is secure on the main PCB.
• Settings check: Some Hyundai models allow disabling the rain sensor in the menu. If the sensor is faulty and you must mow urgently, you can temporarily disable it, but replace the sensor as soon as possible to protect the mower.