Quick answer: Compare a normal computer print, a flatbed scan and an automatic-feeder scan. A line only in feeder scans points toward the feeder’s narrow glass strip rather than the ink or toner.
Use three outputs to isolate the source
Changing ink cartridges is a poor first test when the defect exists in the scanned file itself. Start with a clean original that has no line on it. View the scan on screen, not just as a printed copy, so you can distinguish a captured defect from an output defect.
- Print a short document from the computer and inspect it.
- Scan the same clean original on the large flatbed glass, if your device has one.
- Scan it through the automatic document feeder (ADF), if supported.
- Label or save the results separately so you can compare where the line appears.
| Comparison | Where to look |
|---|---|
| Computer print clean; ADF scan has a line | ADF scan glass and feeder-related parts. |
| Only flatbed scan has a defect | Main glass, original placement and lid backing. |
| Computer print also has streaks | Investigate printing as a separate or additional fault. |
| Same mark visible on the original | The scanner may be reproducing it correctly. |
Find the glass used by the document feeder
Many all-in-ones have a narrow strip of glass beside the larger flatbed. During feeder scanning the sheet passes over this stationary reading area. A small mark there can become a long line in the resulting image. Some two-sided feeders have a second scanning surface; identify it in the exact model’s manual.
Clean without adding a new defect
- Follow the manufacturer’s instructions for shutting down and safely opening the scanner.
- Use a soft lint-free cloth with the approved amount and type of cleaner or water.
- Apply liquid to the cloth, not directly onto the machine or glass.
- Clean the relevant glass and accessible backing gently, then dry them as instructed.
- Repeat the same scan and compare it with the saved baseline.
Do not use abrasives, blades or unapproved solvents. Do not remove the glass or casing to reach an apparent mark beneath it. A scratch is not dirt and will not improve with harder scrubbing. The approved cleaning products can differ by surface and model.
If the line remains
Check whether it stays in the same position across several clean originals and whether it appears on one or both scanned sides. Those observations help support identify the affected scan path. Repeat the comparison after a restart if the model’s guidance recommends it, but avoid changing resolution and cleaning several areas at once without retaining a baseline.
A usable workaround while waiting for service
If flatbed scans are clean, use the flatbed for important documents when practical. Check the full saved image before sending it. This does not repair the feeder, but it can avoid distributing unreadable pages while the hardware is inspected.
Send support the model, labelled comparison images and whether cleaning changed the defect. Use a non-sensitive test document rather than a customer’s record.
Related troubleshooting
- White Lines or Streaks in Inkjet Prints: Read the Nozzle Test
- Printer Prints Blank Pages: Test the Printer Before the Document
Official references
Reviewed against the linked documentation on October 7, 2026. Menu names and supported features vary by model and software version. This guide is independent; it does not claim hands-on testing of every printer.
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