Brother HL-4570CDW: Reset toner cartridge to "full"

2017-08-20: my HL-4570CDW reports "Replace toner Y M C" although my records show that the cartridges can not be empty. Nevertheless I order a new set. Weighting both a new and a supposedly empty cartridges shows a difference of only 8 grams which for me is an indication that it is really just supposedly empty.

HL-4570 specifics

• There exists a Waste Toner box (50 000 pages).
• The 'eyes' F to look through the cartridge are just for fun. Hence black tape is useless.
• Menu functions seem to depend on the exact firmware-level. Hence advice like the following did not work:
• Open the front cover (toner bay).
• Press the Cancel and Secure buttons simultaneously until you see the reset menu appear.
• Press the OK button.
• Press the up arrow and note the word Accept.
• Press OK again.
• You're good to go.

Solution to the problem

Others suggest to reset the flag gear at the cartridge. Thanks to the newly purchased item I can see the difference:

New cartidge	Supposedly empty cartridge
The gear with the 'flag' Spring Drive gear Intermittent gear Cam 'Eye' allowing to look through the cartridge

Compare the location of the 'flag' on gear A and also look at the position of the cam E at gear A: for the "empty" cartridge it is to the left of the stop.

Procedure to reset the cartridge to "full"

1. Find a good stand for the cartridge and avoid touching the toner roller.
2. Remove 3 PH3-screws and carefully lift the gear housing.
3. Lift off gear D to make A and C freely rotatable.
4. Watch how the spring B is engaged in the gear A. It is under a small hook.
5. Unhook spring B - you do not need pliers for this.
6. Rotate gear A clockwise until the cam is to the right of the stop and gear A is engaged with the inner gear of C.
7. Re-apply the spring B. It must be below the hook.
8. Re-apply gear D to block gears A and C.
9. Re-apply the gear housing with the 3 screws.
10. Insert the cartridge and close the front door.
11. The cartridge will be reported to be full again.
12. Take the printer report only as an indication. Judge the level of toner by test pages.