My window cleaning robot leaves streaks after every pass
Home Nura guide — category: Window Cleaning Robots
Diagnosis
A window cleaning robot that leaves streaks nearly always has a dirty or worn pad, or is using the wrong amount of cleaning solution. Streaks appear when dirt just gets moved around and the water dries too fast, especially on warm glass or glass with hard-water stains.
Possible causes
- Dirty or worn pad — it no longer holds on to grime and redeposits it as fine lines on every pass.
- Too much water or cleaner — the excess runs down, dries in drops and leaves rings or drips along the bottom of the glass.
- Glass in direct sun — the solution dries before it's wiped and leaves white streaks of mineral scale or soap.
- Very dirty glass or a greasy film — one pass isn't enough, and the dirt gets spread around instead of picked up.
What to do
- 1Remove the pad, hand-wash it in warm, soapy water without fabric softener, rinse it well and let it dry before putting it back.
- 2Wipe the frame and sills with a damp cloth first, so the robot doesn't smear dust and grit across the glass.
- 3Clean windows in the shade or on a cloudy day, and spray a moderate amount of the manufacturer's recommended cleaner.
- 4For very dirty or greasy glass, run a first cycle with little cleaner, then a second with a clean pad.
- 5Rinse the drive tracks and suction seal with clean water, and check that the pad is held taut by its fasteners.
Repair or replace?
If streaks persist with a new pad and a suitable cleaner, check the suction and the condition of the seal. A robot that keeps losing power or has a warped seal is rarely worth repairing and is better replaced.
If you're replacing it
Window Cleaning Robots: the picks from our buying guide
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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
Dual spray, 8 modes, app and remote control, a safety rope and a backup battery that lasts roughly 30 minutes in a power outage.
Photo: © Cecotec
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Best for frameless glass
Hobot 2S
Compact and light, two ultrasonic nozzles, edge sensor, a 15 ft (4.5 m) safety rope and a backup battery that lasts up to 20 minutes.
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Other common problems in this category
These issues affect the same type of appliance — each one comes with a diagnosis and the steps to take.
- Window Cleaning RobotsMy window cleaning robot keeps losing its grip and almost falls
- Window Cleaning RobotsMy window cleaning robot beeps nonstop and says suction is low
- Window Cleaning RobotsMy window cleaning robot leaves a streak down the middle of the glass on every pass
- Window Cleaning RobotsMy window cleaning robot is losing suction and sliding down the glass
Frequently asked questions
Check the manufacturer's warranty first: how long it lasts and what it covers vary by brand and model, so read the terms for yours and keep your proof of purchase. If you bought it new in the EU, a two-year legal guarantee also applies (Directive (EU) 2019/771), covering defects present at delivery, whenever they first show up.
If you're still within the seller's return window, a return or exchange is usually the fastest fix. After that, go through the manufacturer's support team: it handles warranty claims and can often repair the unit even after the warranty has run out. Either way, keep your proof of purchase.
Our public methodology lowers the Nura Score /10 of any model in our Window Cleaning Robots guide whose recurring failures show up in owner reviews. A model that breaks down too often never makes it to the top, whatever the brand.
Generally, yes, if you stick to routine maintenance: cleaning, replacing a gasket, recalibrating. Irreversible changes to the hardware are what can cause problems, so read your warranty terms before you open anything up. Anything the manufacturer's manual walks you through is the safe zone.
Your proof of purchase, the exact model name and a record of the symptom: photos, a short video, the sound it makes and any error code. Note when the problem started and what you've already tried. With all that in hand, support can pin down the problem much faster.