Message on Brother MFC 7340 is "Toner Life End.Replace Toner cartridge". Plenty of tone in cartridge. Inhfact, I just installed a compatible cartride unit which works fine on a Brother printer. The message: "Toner near end of life" had been a previous nuisance.

The problem with this is the design. Each toner cartridge has a microchip on it, that counts the pages you print. The company has determined that you get x amounts of prints. Then you have to replace it, empty or not. This printers do not work the same way as an expensive professional business copier. In an pro style there is a spent toner cartridge that collects all of the wasted toner that is on the drum. On a small business/home style this spent toner goes back into the cartridge. There is no level indicator, even on the inkjet printer. They too, have a chip that says you have x amount of prints/cleaning cycles they can go through. Look up inkjet refill kits or inkjet cartridge programmer.

some copy cartridges dont work best stick to originals

I got this same error message on a newly acquired Brother DCP-7040 that I purchased used off of ebay.

As I was troubleshooting this unit (that I bought untested off of ebay - hey gambling has paid off handsomely for me many times before!), this error message kept popping up.

I checked the COUNTERS (page & Drum life) and found out that the DRUM had 0% life left. BUT, the reason it showed ZERO was because this unit did not have any drum! The toner cartridge (TN-360) needs to sit WITHIN the drum (DR-360) on this DCP-7040 unit, as well as in models DCP-7030, MFC-7340, MFC-7345C, and MFC-7440N.

So perhaps some of these "put the black toner cartridge back in" problems could be related to the DRUM (or lack thereof). A possible tipoff (since the toner cartridge actually does slide into the unit much like other units that do not use Brother's DRUM carrier) seems to be the relative ease with which the toner cartridge slides into the DCP-7040 and really doesn't seem to "lock" into position real firmly.

DCP-7040 USER GUIDES: http://welcome.solutions.brother.com/bsc/public/us/us/en/doc/manual_index.html?reg=us&type2=-1&prod=dcp7040_us_as&c=us&lang=en&flang=all

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As posted by another before. Remove toner cartridge and cover small window in RHS with opaque tape eg black gaffer tape.

If you open the front cover of your printer where you install the toner cartridge and press the "Clear/Back" button with it open, an option comes up on your LCD Display that says "Replace Drum?" press 1 to reset it. That should fix your problem!

You could try resetting the toner cartridge settings. OPen the machines front door where you would replace the cartridges. On the top panel you will see a "clear/back" button. Press it and on the display you will see a reset menu come up. Arrow to each one and hit the OK button. Press "1" to reset. Once you have gone through all close the front door of the machine and press stop to bring the display back to normal.

Hope this helps.

Is this a genuine Brother replacement cartridge, if not you may find that it is not recognised by your MFC. Also worth a try is removing and reinstalling the new cartridge ensuring all protective packaging is removed. Also remove and reinstall the Drum unit as Brother actually recommend this as part of a new toner install

http://www.brother-usa.com/ModelDocuments/Consumer/Users%20Manual/UM_MFC_7420_7820N_EN_1156.PDF

open front cover, press OPTION button, on the LCD will appear a message "NEW DRUM?" ....DO NOT RESPOND....just type on the keyboard "*00" and there will appear a message "Accepted" and use it in your pleasure.

PS. in any case i blocked with paper labels the viewing windows from transparent plastic on the toner itself....

Mr. Brother, do not try to be smarter than your customer

I just solved my own problem. Try it for yours. I had been using several compatible toners for the MFC-8460N with no problems until today, as I posted earlier. On a hunch, I went to the local office supply store and purchased one original Brothers TN550 toner and put it into the printer and closed the cover. Everything clicked. Toner End Life message gone. I then took that Brother toner out and put the compatible one back in and still everything was fine. Am keeping the original Brother toner as a "kickstarter" if it happens again.