Robot vacuum reports 'Error 3' / voice prompt 'Error 3: Cliff sensor error' and refuses to move or backs up repeatedly.

Safety first: Turn off the robot and keep it away from stairs while testing.

• 1. Clean the cliff sensors:
  • Flip the robot over.
  • Locate the small dark windows along the front and sides of the underside (usually 4–6 sensors).
  • Use a soft, dry cloth or cotton swab to gently clean each sensor window.
• 2. Check the environment:
  • Avoid testing on very dark, glossy, or mirror-like floors that can confuse IR sensors.
  • Move the robot away from direct sunlight or strong spotlights.
• 3. Reboot and test:
  • Power cycle the robot.
  • Start a spot clean on a light-colored, non-reflective floor.
• 4. Advanced inspection:
  • Remove the bottom cover to access the cliff sensor board.
  • Check that the sensor board cable is firmly connected to the mainboard.
  • Inspect the board for liquid damage or corrosion.
• 5. Replacement:
  • If one or more sensors are physically damaged or the error persists after cleaning, replace the cliff sensor board assembly.