Diagnosis
The "humming" or grinding noise you hear is the scanner motor attempting to engage the carriage, but the carriage is physically unable to slide across the scan bed. In the Canon PIXMA MG3620, this is typically caused by a "carriage jam" where the scan head has slipped off its rail or a piece of debris (like a staple or a fragment of plastic) has lodged in the drive mechanism. Because the motor continues to push against a locked carriage, you hear a repetitive mechanical buzzing sound. Alternatively, this can be caused by a failure in the white plastic drive gear or a perished rubber drive belt. If the gear has stripped or the belt has snapped, the motor will spin freely or struggle to grip, resulting in a noise without any corresponding movement of the scan head. You can confirm this by attempting to initiate a scan; if the light bar doesn't illuminate or move even a millimeter, the issue is purely mechanical rather than a software driver failure.
How to Fix It
To resolve a mechanical jam in the MG3620 scanner unit, follow these precise steps:
- Power down the printer completely and unplug the AC power cord from the wall outlet to prevent electrical shock or accidental motor engagement.
- Lift the scanner lid. Carefully inspect the glass surface for any cracks or protrusions that might be hindering the carriage.
- Using a flashlight, look at the right-hand side of the scanner assembly. You will see the scan head (the bar with the light) and a white plastic guide rail.
- Gently place your finger on the scan head and apply a very slight amount of pressure to push it toward the center of the glass. If it is jammed, you may feel a "click" as it pops back onto the rail.
- Check the drive gear on the far right. If you see a small piece of plastic or a foreign object wedged in the gear teeth, use a pair of fine-tipped tweezers to remove it.
- Slowly slide the carriage manually from the far right to the far left. It should glide smoothly without any resistance. If it catches in one specific spot, inspect the rail for bends or debris.
- Plug the printer back in and perform a "Power Cycle" by holding the power button for 5 seconds, then restarting. Attempt a test scan to see if the carriage now homes correctly.
If That Didn't Work
- Reset the Scanner Hardware: Perform a hard reset by unplugging the power cord and the USB cable. Hold the power button down for 30 seconds to drain the internal capacitors. Plug only the power back in and attempt to scan. This can sometimes clear a "stuck" logic state in the scanner's home position sensor.
- Check the Ribbon Cable: If the carriage moves but the computer says "Scanner not found," the flatbed ribbon cable (the wide, white flexible strip) may have a hairline tear. Open the outer casing and inspect the cable for creases or pinches. If the cable is frayed, the unit requires a replacement ribbon cable part, as these cannot be soldered.
- Update the Scan Driver: In some cases, a corrupted MP Drivers package can send conflicting signals to the motor. Uninstall the current Canon MG3600 series driver from your Control Panel, restart your PC, and install the latest "MP Drivers" package specifically for the MG3620.
- Check for "Lock" Switches: While rare on this specific model, ensure no shipping tape or plastic orange spacers were left inside the scanner bed from the original packaging, as these can block the carriage path.
Heads Up
- Never force the scan carriage with excessive pressure; the plastic rails are fragile and can snap, which renders the entire scanner assembly unrepairable.
- Avoid using canned air directly into the gear mechanism, as this can push dust and debris deeper into the motor housing.
- Keep the scanner glass clean using a microfiber cloth and a small amount of isopropyl alcohol; fingerprints or grime on the glass can occasionally cause the auto-calibration sensor to fail, triggering a stop in movement.
- Always unplug the unit before touching the internal components to avoid shorting the logic board.