Sorry, I can't teach you what every part does in a copier.
If you really want to learn about the technology try something like this and go on from there.
I feel like you are questioning me like you are trying to either prove me wrong (which I have fully admitted multiple times anyway) or that I am just trying to make you spend money (which I have in near every post tried to steer you away from)
When you look at the maintenance kit, almost none of it applies, obviously the rollers feed the paper, they play no part in the image quality (except to make sure the paper is in place to receive it, but there is a transfer roll assembly in there, which is what puts a static charge on the paper (which tells the toner where to stick) and tells the drum the same (using an opposite charge)
Then after the toner is applied to the page, it gets run through the fuser, which heats it to the melting point and "fuses" it to the paper.
I asked a co-worker his ideas on the matter, he thinks there is a 60% chance the maintenance kit is the answer, but the other 40% he thinks is a control board, and there is no chance you would be able to find out which one, where to get it, or even how to replace it, at a cost worth doing.
So at this point, you are paying $100 to have a guestimated 60% chance of printing darker.
There is the toner, the maintenance kit and the fuser.
You replaced the first leaving the last 2.
Fuser would likely mean the toner would not stick to the paper, which leaves the maintenance kit.
But there are no 100% answers.
It should not be the maintenance kit, but it could be due to age (you are a long way from 200,000 impressions)
Realistically, due to the cost of that one part, and the fact you cannot be guaranteed it will fix it, I'd seriously consider another printer before I would by the part. Especially since you could buy a complete color printer for less that has way more features.
This is in regards to a Xerox Phaser 4500N that was purchased new around 2004 and has printed approximately 8,500 pages.
The print output is light - like 50% gray.
The toner cartridge has been replaced with a new 113R00656 cartridge and currently has about 95% toner left.
In addition, the printer experienced a bootup error and the laser assembly (084K13154) was replaced which corrected the error.
The NVRAM has been reset multiple times.
However, the print output is still light.
This printer has never had a Xerox maintenance kit (108R00600) installed.
Is the fix the maintenance kit ?