When I install toner on my Lexmark MS510dn, why is it blocked by a flap on the imaging unit?

The Issue

A flap on the imaging unit covers the toner port to keep toner from making a mess while the toner cartridge is out of the printer during replacement. When the new toner cartridge is inserted into the machine, the toner supply port on the toner cartridge has to be inserted under the flap on the imaging unit. This affects the following models: Lexmark MS310d / MS310dn / MS312dn / MS315dn / MS410d / MS410dn / MS415dn / MS510dn / MS610de / MS610dn / MS610dte / MS610dtn

The Resolution

When inserting the new toner cartridge, care must be taken to open the flap with the toner supply port on the new toner cartridge.

The following steps should be used when replacing the cartridge:

1. Remove the toner seal strip
2. Insert the toner cartridge into the printer with the imaging unit already in place. Be sure to slide the toner supply port under the flap on the imaging unit. (The following photos show the toner cartridge and imaging unit outside of the printer to provide a better view of the important details.)
   501H toner cartridge approaching the toner flap on the imaging unit (this would normally be done inside the printer)
   
   Toner cartridge supply port sliding under flap on the imaging unit (this would normally be done inside the printer)
   
   Toner cartridge supply port fully inserted under flap on the imaging unit (this would normally be done inside the printer)

Additional Notes

If you currently use, or are interested in using, compatible brand toner cartridges, you may wish to do research before upgrading or allowing a service person to upgrade the printer’s firmware. According to some sources, one of the recent firmware upgrades includes an update to block the use of non-genuine toner cartridges.