Robot vacuum beeps and shows E3, often when approaching stairs or dark carpets.

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

• Clean cliff sensors: Locate the small infrared windows on the underside front edge (usually 3–6 sensors). Wipe each sensor window with a soft, dry microfiber cloth. For stubborn dirt, lightly dampen the cloth with water and dry immediately.
• Check for reflective or dark surfaces: Very dark or glossy floors and black carpets can confuse cliff sensors. Test the robot on a light-colored, matte hard floor.
• Inspect sensor openings: Make sure no tape, stickers, or aftermarket bumpers are covering the sensor windows.
• Reboot the robot: Turn the main power switch OFF for 30 seconds, then ON again. Start a short cleaning run in an open area.
• If E3 persists: A cliff sensor or its wiring may be defective. The cliff sensor array or bottom sensor harness may need replacement, which requires opening the bottom shell and disconnecting the sensor board from the main PCB.