Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
The Brother 4100e is a laser fax machine. This means it has laser-printer-type problems at times, which I am quite thoroughly familiar with and practiced with, all the way back to 1988 when I started working on laser printers and their problems.
The things that can cause an all-black page in a laser-type printer (or fax) are pretty much three:
1. the toner cartridge. This is most likely and most common.
2. the high voltage power supply might be defective (or, not transmitting to the right electrode in the printing engine of the laser printing machine...about this, more in a moment.) If there is no high voltage delivered to the print engine, the toner is attracted *to* the page (or, the drum and thence to the page), but not *from* it.
It might be a matter of transmission... if the HVPS is OK, but the line from it is broken or, more likely, the electode is obscured by grease or heavy toner scattering, which can diminish the voltage transmitted or block it completely... same result either way.
So cleaning the printer's inside parts is crucial here: especially (with the power Off and unplugged, so as not to risk high voltage shock!) any metal contacts in the paper path and in the print engine and leading to the toner cartridge when the toner cartridge is in.
So turn Off, unplug, remove the toner cartridge, and wipe quite clean, with a clean dry rag cloth, any metal contacts esp. those near where the toner cartridge goes into its place.
Note: do not even touch, much less clean off, the 'drum' - which may at present be caked with toner, or not. But touching it ruins it, breaks it, irrevocably - and then you need another one, at expense. Of course in some, and probably in your model, the 'drum' is included in the toner cartridge.
3. also, the logic circuitry can be locked into an all-black printout state. But that's rare, too.
So it most likely is the toner cartridge. Esp. if the cartridge is 3 years without use... laser printer supplies can last awhile, but occasionally, definitely not. 3 years is a while.
But clean it first according to my instructions and try once again, before replacing the toner cartridge.
Let me know how it goes, please. Thanks.