How to Fix Gray or Black Bars When Scanning on Epson WF-3640 or WF-3620 Printers

Question:
When scanning with my Epson WF-3640, a gray or black bar appears on the right side of the scanned image. The scanner lights seem to be working and moving normally across the document. Does this mean I need to replace the entire scanner unit?

Answer:

When a gray or black bar appears on one side of your scanned image-especially on Epson WorkForce Series printers like the WF-3640 or WF-3620-it's often caused by optical or mechanical issues rather than a full scanner failure. The good news is, in most cases, you don't have to replace the entire scanner unit. Here's how to identify and potentially fix the problem.

1. Clean the Scanner Glass and Calibration Area

The most common cause of a black or gray bar is dirt or residue on the scanner glass, especially near the calibration strip at the far edge of the glass (usually under the plastic frame). When dust, correction fluid, or ink overspray collects there, the scanner's sensor can't properly calibrate the white balance, causing a dark strip on every scanned image.

• Use a lint-free cloth and a small amount of glass cleaner (never spray directly on the glass).

• Pay extra attention to the narrow strip of glass used for document feeding if you're scanning through the Automatic Document Feeder (ADF).

• If you're using the flatbed scanner, clean both the main glass and the white backing underneath the scanner lid.

2. Test the Automatic Document Feeder (ADF) vs. Flatbed

If the gray bar appears only when using the ADF, the issue could be with the ADF scanner strip, which is separate from the flatbed's main glass.

• Try scanning a page using the flatbed to see if the problem disappears.

• If the flatbed works fine, clean the narrow glass strip located near the paper feed area where documents pass through during ADF scanning.

• Make sure there's no paper dust, toner residue, or tape adhesive buildup on that narrow strip.

3. Check for Scanner Light and Mirror Alignment Issues

You mentioned that the scanner lights are all on and moving normally, which is a good sign-the light source is functioning. However, if the mirrors inside the scanner carriage are misaligned or if dust has accumulated on them, the sensor may fail to read one side correctly. This misalignment can also cause a partial scan blackout.
If cleaning doesn't help, gently check that the scanner bar moves evenly across the entire width of the glass. If it jerks or stalls at one side, it may indicate a stepper motor or timing belt issue inside the scanner assembly.

4. Consider Replacing the Scanner Unit Only if Necessary

If you've cleaned the glass thoroughly and the issue persists on both the flatbed and ADF, then it may be time to consider replacing the scanner unit. Epson scanners are integrated into the printer's upper housing, but the part can be replaced separately. We have a step-by-step video guide showing how to remove and replace the Epson WF-3640 and WF-3620 ADF scanner: Watch the tutorial here (https://www.youtube.com/watch?v=ENOdkkVnpwY).
This video demonstrates how to detach the top scanner assembly safely without damaging the cables or hinge sensors.

Addressing printer issues can be a complex process because they often require hands-on inspection. For that reason, we're unable to offer remote troubleshooting or repair support. However, we do provide in-person evaluation and repair services at our local diagnostic facility (https://bchtechnologies.com/printer-repair-service). Our repair queue runs on a first-come, first-served basis, and depending on the demand, there might be a waiting period of a few weeks before drop-off. We repair both entire printers and individual components, offering clear instructions for next steps. While our rates reflect the quality and expertise of our service, we understand some customers prefer a DIY approach. In that case, we highly recommend exploring our YouTube channel (https://youtube.com/@bchtechnologies) for self-help videos. Use the search icon next to "About" on the channel's menu bar to find videos related to your model or issue-searching "WF-3640 scanner" or "ADF replacement" will bring up the most relevant tutorials.

Thank you again for your patience and for taking the time to reach out. We appreciate your continued trust in BCH Technologies and hope these steps help get your Epson scanner back to full performance.