Black line through every page on HP Officejet 8500 A909a

[Aya0805]

We've had this printer for a while at the Office and not even a week ago it started printing with a black line through every page. Normally that would constitute a problem with the cleaner head. WRONG! It's not the cleaner head. It will print from the computer without the black line and when something is printed from the glass scanner it won't show a black line through my documents. The only time it shows up is when I print copies from the tray. It also happens when we fax some of our documents to some of our important clients and companies.

We NEED this to work. What could possibly be the issue? This has got to be fixed AS SOON AS POSSIBLE! It's beyond urgent that I get a reply on what I can do for this printer. Faxes must be sent daily from our Office. I have files just piling up on my desk. HELP! 

Thank you!

[Bob_Headrick · Accepted solution]

There is a small (about 1" wide) section of glass that is used for the ADF scanning.  It is just to the left of the main glass, see this post for details.  A spot on this glass will turn into a line as the paper is fed past it by the document feeder.  Cleaning this section should resolve the issue.

[Bob_Headrick]

I found a picture, page 185 of the user manual here has cleaning instructions for the glass.

In the diagram the glass that is causing the problem is the thin section with the arrow pointing to it below:

[Aya0805]

Thank you soooooo much! <3 You are some kind of amazing!