Robot mower displays E8 and refuses to start; often after rain or washing.

Safety first: Turn OFF the mower and disconnect the battery. Do not operate the mower in heavy rain or standing water.

Steps to clear:

• 1. Confirm weather conditions: If the lawn is wet or it is raining, allow the area to dry. Yard Force rain sensors are designed to prevent mowing on wet grass.
• 2. Clean rain sensor: Locate the rain sensor (often on the top housing or under a small grille). Remove debris, leaves, and dirt. Ensure any drain holes are clear.
• 3. Dry the mower: Move the mower indoors to a dry, ventilated area for 24 hours. Remove the top cover and allow internal components to dry if there are signs of condensation.
• 4. Inspect sensor wiring: Check the rain sensor cable and connector on the main PCB for corrosion or loose fit.
• 5. Sensor test: With the mower powered (and blades disabled), lightly wet the sensor with a damp cloth and observe if the status changes, then dry it. If the sensor always reads "wet" even when dry, it is likely faulty.
• 6. Replace rain sensor: Install a new Yard Force rain sensor module if the old one is defective.