Some cliff sensors interpret very dark patterns as a drop. Cleaning sensors and checking model-specific settings is safer than covering the sensors. Lay a light-colored cloth over a section of the rug; if the robot crosses that, the sensor is reacting to the dark color.
What this covers
- Robot vacuums · cliff sensors
What it does not cover
Differential
Likely causes of “Robot vacuum will not cross a dark rug”, and how to tell them apart
- 1
The cliff sensors read a very dark rug as a drop
What separates it The robot stops or backs up exactly at the dark edge and shows a cliff or drop warning in the app.
How to confirm Lay a light-colored cloth over a section of the rug; if the robot crosses that, the sensor is reacting to the dark color.
- 2
Dirty cliff sensors make the reading worse
What separates it The robot behaves erratically near several dark or shiny spots, and the sensors on the underside look dusty.
How to confirm Wipe each cliff sensor on the underside of the robot with a dry cloth and retest.
- 3
A model setting controls how sensitive the sensors are
What separates it The app offers a carpet or surface option that has not been turned on.
How to confirm Look in the app settings for a surface or carpet-detection option for your model.
Before you touch a setting
Record this first — changing settings destroys the evidence
- Whether the robot stops at the edge or partway across the rug.
- The rug color and pattern, and whether other dark surfaces cause the same stop.
- Any cliff or drop message in the app at the time.
Try in this order
0 of 4 completedObserve before changing anything
ReversibleObserve whether the robot stops exactly at dark sections and reports a cliff or drop warning.
Isolate the failing boundary
ReversibleClean sensors and improve lighting, then check whether the manufacturer provides an approved carpet or sensitivity setting.
Apply the narrow correction
ReversibleUse a physical boundary or alternate cleaning method if the surface remains unsupported.
Verify the result and stop at the boundary
ReversibleDo not tape over cliff sensors; that can allow the robot to fall down stairs.
Stop boundary
When this stops being a self-service repair
- !Do not tape over cliff sensors: the robot can then drive off a stair edge. Use a physical boundary or the maker's approved setting.
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Is it safe to cover the rug with a lighter cloth?+
Only as a short test. It does not fix the sensor, so for regular use choose a rug that the robot can cross, or use a boundary that keeps it off.
Why not the dark rug?+
Cliff sensors read dark as a drop.
Can tape help?+
Some use it carefully.