I've fully dismantled my Neato XV-21 to locate the source of the "can't see" problem. (And also replaced a tight wheel Motor causing a "something is caught in my right wheel" message)
There several screws underneath the Neato XV-21 that must be undone to allow the top to be separated. A bit of a pain just to get into the visual sensor area. But not too hard with an electric screwdriver.
There is a Laser device & a Photo sensor mounted to a black plastic rotating wheel which is covered by a black cap with 2 holes in it. One hole for laser beam to exit & one to pick up return laser light return data. They are both rotated by a motor & pulley via a rubber "o" ring which could slip, break or get hairs caught in it.
These could be the source of problems. Once mine was cleaned & checked I had no more problems. Then the wheel motor got tight. Replacing the motor fixed the problem. This requires hoping the Motor Gear Box assembly out by poping the pivot shaft out of it's plastic holder. Then disconnect the spring & cable connector. But you bust be prepared to carefully remove the magnet off the motor shaft (vice & 2 flat blade screw drivers) then unsolder the small PCB at 2 points. With practice (twice) I can now replace a motor in 20-30 minutes.
Hope this Helps some Neato Users out there
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