u4fi-4120C

Fujitsu fi-4120C Scanner U4 Error: Cover Fault

The Fujitsu fi-4120C Scanner error U4 alerts that the top cover is not detected as closed. For safety, the device disables movement when it detects an open housing. This error is easy to resolve by adjusting the closure or removing obstructions that prevent the sensor from registering the lid contact.

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Common causes

  • 1Incomplete closure: Cover not fully seated in position.
  • 2Obstruction: Paper scraps interfering with the safety switch.
  • 3Plastic wear: Worn latches failing to press the sensor fully.
  • 4Defective sensor: Electronic failure in the safety switch.

Solutions

Quick Diagnosis

If you firmly close the lid and the U4 error persists, the safety switch may be blocked. Check that no paper is stuck in the hinges or the latch mechanism.

Step-by-Step Solution

  1. Open the lid and ensure the interior is clear of any debris.
  2. Verify that the plastic latches are not broken or bent.
  3. Close the lid and listen for a clear 'click' of the latch engaging.
  4. If the issue remains, clean the small switch located near the hinge.

Prevention and Maintenance

Handle the cover gently. Avoid slamming the lid, as the safety sensors are delicate plastic components. Keep the hinge area free of dust.

When to Call a Technician

If the scanner continues to report U4 despite verifying the path is clear, the cover’s electronic safety switch is likely faulty.

Device Technical Specifications

  • Technology: Duplex scanner
  • Sensors: Cover position sensor
  • Connectivity: USB 2.0
  • Consumables: Roller kit (Feed rollers)
  • Recommended Use: Document digitization
  • Drivers / official firmware

Steps to follow

  1. 1

    Verify Closure

    Open and firmly close the lid to ensure the latch engages correctly.

  2. 2

    Check Obstructions

    Remove any paper scraps preventing the lid from closing flush.

  3. 3

    Clean Sensor

    Clean the cover safety switch with a dry cloth to remove dust.

Frequently asked questions

The U4 indicates that the device does not detect the top cover in a closed position.

Often, dust or a small scrap of paper prevents the cover from contacting the sensor.

Do not attempt to force it; if it doesn't close properly, check for obstructions before applying pressure.

Only basic cleaning to ensure the plastic latches are not damaged by excessive pressure.

Fujitsu fi-4120C Scanner U4 Error: Cover Fault | Vimazdev