Question : Problem: HP laserjet showing Black smudges

I have a hp laserjet 4350dtn that after I have change to toner cartridge the printer still shows black smudges. The printer does not show time for maintenance kit. Any clues?

Answer : Problem: HP laserjet showing Black smudges

If the print defect is ghosting or repeat info on the page then it is most likely the fuser unit. Take the fuser out and examine it. You will probably find that one or both of the rollers have toner caked to them.
You can change the fuser any time it needs to be. You also don't need to change it every time the printer tells you to. I never change the fusers until they have a problem. Usually the problem is ghost printing because of toner build up.