My window-cleaning robot leaves a streak in the centre of the glass every pass
Home Nura guide — category: Window Cleaning Robots
Diagnosis
A streak down the middle of the glass is almost always caused by a dirty cleaning pad or by grime collecting along the robot's centre line. The robot drags dust inward and then smears it back and forth on every pass instead of pushing it out to the edges.
Possible causes
- Pad saturated with dirt — it wipes poorly at the robot's centre, where pressure is highest, and leaves a dark band behind.
- Pad attached loosely or creased — a fold leaves a sharp line that repeats in exactly the same spot on every pass.
- Very dusty glass to begin with — the robot gathers the dirt into a central ridge and keeps running over it without absorbing it.
- Too little cleaning liquid — the pad dries out mid-run and rubs the dirt around instead of dissolving it.
Recommended steps
- 1Switch off and unplug the robot, remove the pad and hand-wash it in warm soapy water without fabric softener, then let it dry fully before reuse.
- 2Check the pad is stretched tight and flat across its full width, following the diagram in the manual.
- 3Wipe the edges and frame of the window with a damp cloth first, so dust and grit are not carried into the middle by the robot.
- 4Spray the manufacturer's recommended cleaner evenly over the pad or glass, without soaking it, so the robot can still grip properly.
- 5Run a second cycle in the criss-cross cleaning pattern, then clean the drive track and the suction seal with a damp cotton swab.
Repair or replace?
If the pad is worn out and the streak stays after a thorough clean, the pad needs replacing, not the robot. Only replace the robot if suction keeps weakening or the tracks slip, because a repair usually costs more than buying a new one.
If you decide to replace it
Window Cleaning Robots: the shortlist from our buying guide
- View on Amazon →
Best overall
Ecovacs Winbot W2 Omni
Portable battery station, self-winding safety cable, three-nozzle spraying and edge detection for frameless glass.
Photo: © ECOVACS
- View on Amazon →
Best value
Cecotec Conga WinDroid 1090 Double Spray Connected
Double spray, 8 modes, app and remote control, safety cord and a roughly 30-minute battery in case of a power outage.
Photo: © Cecotec
- View on Amazon →
Best for frameless glass
Hobot 2S
Compact and light, two ultrasonic nozzles, edge sensor, 4.5 m rope and a backup battery lasting up to 20 minutes.
As an Amazon Associate I earn from qualifying purchases. Amazon affiliate links: commission at no extra cost to you.
Other common problems in this category
These issues affect the same type of appliance — each one comes with a diagnosis and the recommended steps.
- Window Cleaning RobotsMy window-cleaning robot keeps losing grip and nearly falls
- Window Cleaning RobotsMy window-cleaning robot leaves streaks after every pass
- Window Cleaning RobotsMy window-cleaning robot beeps non-stop and reports low suction
- Window Cleaning RobotsThe suction pad on my window-cleaning robot is losing grip and the unit slides
Frequently asked questions
Usually, yes, if the failure shows up during the warranty period and isn't caused by misuse. A product in the Window Cleaning Robots category bought new from an authorized retailer normally comes with a manufacturer's warranty: check its length in the manual or on the brand's website. Consumer protection rules also vary by province and territory, so keep your proof of purchase.
If you're still within the store's return window, a return or exchange is usually the fastest fix. After that, the manufacturer's warranty takes over: its customer support can arrange a repair or a replacement. Even outside the warranty, the manufacturer can often repair the device for a fee. Either way, keep your proof of purchase.
Our public methodology lowers the Nura Score /10 of any model in the Window Cleaning Robots category whose recurring failures are documented in owner reviews. A model that breaks down too often never tops our rankings, whatever the brand.
Generally, yes. Routine maintenance, such as cleaning, replacing a gasket or recalibrating, is part of normal use and doesn't usually affect your warranty. Irreversible changes to the hardware are what can cause problems. For a product in the Window Cleaning Robots category, stick to the steps described in the manufacturer's manual and read the warranty terms before going any further.
When a product fails in its first few months of normal use, the cause is usually a manufacturing defect. Contact the seller or the manufacturer with your proof of purchase and a description of the symptom: for a model in the Window Cleaning Robots category that is still under warranty, this is the typical case for a free repair or replacement. Warranty terms vary by brand, so read yours.