Applies to: ADF versus flatbed diagnosis. Cleaning products and disassembly steps must follow the exact device manual.
If the line appears in the same position on every feeder scan, inspect and clean the narrow ADF scanner strip. Turn off and unplug the device first, use a lint-free cloth, and follow the manufacturer’s cleaning instructions. Never spray liquid directly on the glass.
Use the line position as a clue
A tiny speck on the narrow feeder glass becomes a continuous vertical line because every part of the page passes over the same point. A mark on the large flatbed glass usually appears as a stationary spot or shape instead.
Scan one page through the feeder and then place the same page on the flatbed. If the line appears only through the feeder, focus on the narrow scanning strip and the matching white backing area.
Clean without forcing the mechanism
Read the device manual before opening an ADF hatch. Turn the device off and disconnect power if instructed. Use a soft, lint-free cloth and only the cleaning method approved for the model.
- Remove paper from the feeder.
- Locate the main glass and any narrow feeder scanning strips.
- Remove loose dust with a clean, dry cloth.
- If permitted, put a small amount of mild glass cleaner on the cloth—not on the scanner.
- Dry the surface completely with a lint-free cloth.
- Reconnect the device and scan the same test page.
Avoid common cleaning mistakes
Do not spray cleaner directly on the glass because liquid can run under the edge and damage the device. Avoid abrasive cleaners and solvents. HP guidance also warns that isopropyl alcohol can leave streaks on scanner glass.
Do not scrape stuck material with a blade. A scratch can create a permanent line and may require service.
When cleaning does not solve it
Recalibrate the scanner if the manufacturer provides a calibration procedure. If the line remains in the same place on both flatbed and feeder scans, or the glass appears scratched or cracked, stop cleaning and contact service.
Keep the before-and-after test scans. They help distinguish a source-document mark from a device fault.
Rotate the source to isolate a document mark
Use an ordinary sheet that is safe for both feeder and flatbed. Scan it, rotate the original 180 degrees, and scan again through the same path. A printed mark on the source moves with the page; a line caused by contamination at a fixed scanner position tends to remain at the same cross-page location.
Record which path shows the problem and keep the two files for support. Duplex scanners may use separate sensors, so a defect on backs only is useful evidence. Do not infer that every visible line means dirty glass: persistent marks after approved cleaning may require service.
Sources and further reading
Vendor instructions and background references are linked below. Worked examples are our explanatory calculations, not vendor performance claims. Check the instructions for your current software and device.
Report a correction with this page’s title and the step or result that needs attention.