Head alignment failed

[ChiaraO]

Hi!

I have a  HP Officejet Pro 8500A - A910a printer.

Every time I try to print something the printer automatically run the "printhead alignment"  but it prints just the first line of the alignement page and then it says "Head alignment failed" and ejects the sheet.

I already tried to:

- clear the printheads

- run a diagnostic page

- manually clear the printheads

- change all the toners

- reset the printer ( disconnet the power with the printer turned on,...)

What can I do?

[Valsimot]

When the printer goes to alignment it prints lines and then reads them with a light sensor, it's possible that you have a defective line sensor that can't read lines on the alignment page and goes to failure.
Unfortunately, there is nothing much you can do, unless you have a spare line sensor for diagnostic purposes.