Epson WF-7720 Scanner Lid Sensor Replacement: How to Fix the "Close Scanner Unit" Error

Question:

I watched your video about fixing the Epson WF-3640 "Close Scanner Unit" error and replacing the LCD panel, and it was very helpful. Where can I purchase the scanner-lid sensor for an Epson WorkForce WF-7720, and how do I replace it?

Answer:

Where to Buy the Epson WF-7720 Scanner-Lid Sensor

You can visit the BCH Technologies website [https://bchtechnologies.com] and use the website's search function to search for "mechanical sensor." The type of part you are looking for may be listed as an Epson Mechanical Open/Close Sensor, cover-open sensor, scanner-unit sensor, or mechanical lever sensor.

You can also review the Epson Mechanical Open/Close Sensor product page [https://bchtechnologies.com/products/epson-cover-open-sensor-for-wf-3640]. This is a small mechanical switch with a movable lever. When the scanner unit is lowered, a plastic actuator on the printer presses the lever and tells the printer that the scanner unit is closed.

However, please compare the replacement part carefully with the sensor already installed in your WF-7720 before ordering. Epson uses similar-looking sensors in several printer models, but the following details may differ:

• Connector type and number of pins

• Lever length and direction

• Mounting-hole position

• Sensor-body dimensions

• Wire-harness length

• Electrical switching configuration

A sensor that looks similar may not necessarily fit or operate correctly. Taking clear photographs of the original sensor, connector, mounting position, and wire routing before removing anything can help you compare the parts.

Confirm That the Sensor Is Actually Causing the Error

Before replacing the sensor, inspect the mechanism that activates it. The "Close Scanner Unit" message does not always mean that the electrical sensor itself has failed. The printer displays the message whenever the mainboard does not receive the expected closed signal.

Possible causes include:

1. The scanner unit is not fully seated.
   Something may be preventing the scanner assembly from lowering completely. Check for foreign objects, loose cables, displaced plastic covers, or ink tubing trapped between the scanner and printer body.

2. The plastic actuator is not pressing the sensor.
   A plastic tab or projection on the scanner unit normally presses the sensor lever when the scanner is closed. If that tab is broken, bent, missing, or misaligned, a new sensor will not solve the problem.

3. The sensor lever is stuck or damaged.
   The small lever should move freely and return to its original position. Dried ink, debris, or physical damage may stop it from moving properly.

4. The sensor has shifted out of position.
   If the printer was previously disassembled, the sensor may not have been installed correctly. Even a small positioning error can prevent the scanner unit from pressing the lever.

5. The wire or connector is loose.
   The sensor's wire harness may have become disconnected, partially seated, pinched, or damaged. Check both ends of the connection when accessible.

6. The mainboard input is damaged.
   If the mechanical sensor and wiring are working correctly, the problem may be farther along the circuit. A damaged connector, broken board trace, or failed input component on the mainboard can cause the printer to continue reporting that the scanner unit is open. In that situation, replacing the sensor alone will not correct the error.

How to Replace the Scanner-Unit Sensor

The exact disassembly procedure may vary depending on where the particular sensor is mounted in the WF-7720. The WF-7720 scanner assembly is larger and heavier than the scanner on the WF-3640, so do not assume that every step in the WF-3640 video will be identical.

The general replacement process is as follows:

1. Turn Off and Unplug the Printer

Turn the WF-7720 off using its power button and wait until it has completed its shutdown process. Unplug the power cord and disconnect the USB, Ethernet, and telephone cables, if applicable.

Do not work inside the printer while it is connected to power. The scanner assembly contains cables and electronic components that can be damaged by accidental short circuits.

2. Remove the Paper and Ink Cartridges if Necessary

Remove loose paper from the rear feed and paper cassettes. Depending on how far you need to disassemble the printer, removing the ink cartridges can reduce the risk of leakage. Keep the cartridges upright and protect the ink outlets from contamination.

3. Open the Scanner Unit and Locate the Sensor

Raise the scanner unit and inspect the areas near the hinges and the upper printer frame. Look for a small black mechanical switch with a movable plastic lever. The sensor is normally positioned where a tab on the scanner assembly can press it when the scanner is lowered.

Before removing anything, slowly lower the scanner unit while watching the suspected sensor. Verify that the scanner's plastic actuator reaches and presses the lever. Keep your fingers clear of the hinges and do not force the scanner downward.

If the actuator does not touch the lever, the issue may be alignment or a broken plastic tab rather than a defective sensor.

4. Remove the Necessary Exterior Covers

Access may require removing one or more side covers, hinge covers, rear covers, or the control-panel assembly. Keep screws organized because Epson often uses screws of different lengths in nearby locations. Installing a long screw in the wrong position can damage plastic parts or internal components.

Photograph every stage of disassembly, including:

• Screw locations

• Cable routing

• Connector orientation

• Grounding contacts

• Sensor position

• Hinge and spring positions

Avoid pulling a cover away quickly. A cable may still be attached underneath it.

5. Disconnect the Sensor

Once you can reach the sensor, identify its connector and wire harness. Disconnect the plug by gripping its plastic housing rather than pulling on the wires.

Check the connector for:

• Bent or corroded contacts

• Ink contamination

• Broken locking tabs

• Loose wires

• Pinched insulation

• Damage where the harness bends around the scanner hinge

A damaged wire near the hinge can create an intermittent problem because the harness moves each time the scanner unit is opened or closed.

6. Remove the Old Sensor

The sensor may be secured with a screw, plastic clips, or both. Release it carefully without breaking the mounting bracket. Pay close attention to the direction of the lever and the orientation of the connector.

Place the old and new sensors side by side. Confirm that their dimensions, mounting points, pin arrangement, lever movement, and connector positions match.

7. Install the Replacement Sensor

Install the new sensor in the same orientation as the original. Make sure it sits completely in its mounting position and cannot rotate or shift when pressed.

Reconnect the harness securely. Route the wire through its original guides and channels so that it cannot be pinched by a cover or hinge.

8. Test the Mechanical Operation Before Reassembly

Before reinstalling every cover, slowly open and close the scanner unit while watching the sensor. Confirm that:

• The scanner's actuator contacts the lever

• The lever moves fully

• The lever returns when the scanner is raised

• The sensor does not shift in its bracket

• The wire does not stretch or become pinched

If you have suitable testing experience, you may also check the sensor with a multimeter. A basic mechanical switch should change electrical state when its lever is pressed. However, do not assume the pin arrangement without identifying the correct contacts.

9. Reassemble and Test the Printer

Reinstall the covers and screws in their original positions. Reconnect the printer and turn it on.

If the "Close Scanner Unit" message disappears, test the printer's basic functions, including printing, scanning, and opening and closing the scanner assembly. If the message remains, recheck the actuator alignment, sensor connector, harness continuity, and mainboard connection.

The Epson WF-7710 and WF-7720 share a service platform, and service documentation for these models includes troubleshooting and disassembly information. However, these procedures are intended for repair personnel and should be followed carefully because incorrect disassembly can damage the scanner cables, hinges, control panel, or mainboard.

Addressing printer issues can be complicated because many problems require hands-on inspection and testing. For that reason, we are unable to provide individualized remote troubleshooting, repair suggestions, or technical support for printer repairs.

We offer in-person evaluation and repair through our local printer diagnostic and repair facility [https://bchtechnologies.com/printer-repair-service]. Due to high demand, repairs are accepted on a first-come, first-served basis, and it may take several weeks before an appointment becomes available for you to drop off your printer. Our services can cover either a complete printer or certain removable components, with instructions provided for the applicable service. Please be aware that professional diagnostic and repair services may not always be the most economical option.

For this reason, we strongly encourage researching the issue and considering self-help resources when appropriate. You can begin with YouTube or visit the homepage of the BCH Technologies YouTube channel [https://youtube.com/@bchtechnologies]. Use the search icon near the "About" section on the right side of the channel's menu bar and enter terms such as "WF-7720 cover sensor," "WF-7720 scanner sensor," "close scanner unit," or "mechanical sensor."

We receive dozens of questions each day asking whether we have videos about specific repairs. Since we have produced repair videos for more than nine years, it can be difficult to remember every video and topic in our library. YouTube's channel-search function is usually the fastest way to locate the most relevant material. It may also recommend helpful videos from other repair channels.

Thank you again for watching our video, contacting BCH Technologies, and taking the time to share your question. We sincerely appreciate your support and hope this information helps you identify the correct sensor and determine whether replacement is necessary.