Bert,

I'll suggest opening both doors and remove drum cartridge, then close front door only (the one you open to replace a toner) and rotate carousel using your hand until it reaches a position where the toner cartridge you want to remove is accessible trough the upper slot: unlock cartridge and remove.

If the printer is still in warranty you should contact Dell and get the left plastic latch replaced to fix the issue.

Regards,

Excellent suggestion - worked just as you said. Thank you.

After removal I was able to rotate the drum assembly and install a new toner cartridge. Re installed the drum, powered up and print some test pages. OK

This printer is over 3 years old, so far out of any warranty. Sadly, I'm going to need a Cyan cartridge soon. So it appears that leaves me with some choices:

Buy a Cyan cartridge, install the same as above and hope for the best.

Time for a new printer.  

Don't print any color so the Cyan doesn't wear out, use up the black cartridge, then go for a new printer. 

Oh well, the 3100 worked great while it lasted. 

Thanks again,

Bert  

Worked for me many thanks.