For the brother mfc 7820N the toner life end pops up and i have tried the *00 to reset and it doesnt work. What do I do?

I fail to see why you are covering up the toner sensor led's when you have a new cartridge fitted?
Also if you are using a recycled toner from a very well known uk shop that refills toners and ink then you may well have broken the drive gear that stirs the toner. i have seen this six times and their toners do this.
It could well be one of the pitfuls of recycled toners.

If you want to reset your Brother MFC 9440N machine so you no longer have the error message: Toner End of Life, do the following:

1. Open the front cover of the 7820N, that is, the cover that allows you to pull out the toner and drum, but don't pull out the drum/toner.
2. Push the button: Options (located on the left of the control pad).
3. Type: *00 on the keypad.

The Brother MFC 9440N should be reset and the Toner End of Life message should disappear. Warning, this may void your warranty and ultimately damage your machine if you are reusing or refilling your cartridges, but you should already know that. Hope this helps.

go to this link and i am not sure but i think the one at the top of the page might help you out.. toner cartridge for the MFC 7820n printer It still says the toner life is...

I found the following post on another site. It appears to work. If you want to reset your Brother MFC 7820N machine so you no longer have the error message: Toner End of Life, do the following:

1. Open the front cover of the 7820N, that is, the cover that allows you to pull out the toner and drum, but don't pull out the drum/toner.
2. Push the button: Options (located on the left of the control pad).
3. Type: *00 on the keypad.

The Brother MFC 7820N should be reset and the Toner End of Life message should disappear. WARNING: This may void your warranty and ultimately damage your machine if you are reusing or refilling your cartridges, but you should already know that. Hope this helps.

Open the front cover of the machine, press the clear/back (or options) button. it will say replace drum? press *00 close the front cover

this will reset the toner cartridge for you.

we can refil toner many times but we should reset cartage, while we refiling toner to open cartage we should sides white rings middle plastick flate white plate make adownof cartage it is first methode. when we put reffiling cartage put on printer and do on at that time we push cartage right side pointo re set. look on www.brother.com

I was having the same problem with my MFC7820N.  To be honest, I think I got a little lucky poking around with a screwdriver, because the problem seemingly dissapeared.  However, I don't recommend it unless you know what your doing.
I did come across this solution on the internet afterwards though:
Open the front cover of the machine (open the compartment where you insert the toner cartridge)  Wait for "front cover open" to show on the screen.  Press the "Options" button, then press *00 and wait a few seconds, then close the front cover.
This resets something or other, I imagine it will work for you.  Hopefully it does, and if so you're welcome :)
Now, if you can just tell me exactly what is causing my MFC7820N to only have a tiny amount of toner stick to the top right of the page, we'll call it even.

While you have the door open, you have to press some buttons on the menu which will reset the counter. Sorry, I forget what they are right now (it's been a while since I've done it), but you can google and I'm sure you will find it.

did you reset the toner life?

open the front cover, press the option button, on the screen will display ''reset toner life 1 yes 2 no ''
press 1 and close the cover.

toner life reseted