Laser Printer Xpert needed

I've googled up a bit and get multiple explainations for my issues, so I thought I might find someone here with first hand knowledge.
I have several LaserJet printer that are:

1) Printing black pages - you can barely make out the text - every once in a whil a nice page makes it out.

2) Printing streaks down the bottom quater of the page.

I have cleaned these units and replaced the toner carts & they seemed to be printing fine for a day....

Any ideas?

 

is the toner getting fused correctly, maybe the fuser is going, or is dirty, you say that you have cleaned them, what did you clean? make sure you clean the fuser and all the rollers. How old are the printers?

 

Make sure you let the printer cool off for a while before you touch any of those rollers!! The fuser get extremely hot and can burn you!!

Roger