Why do I get a thick black line down side of page when copying, but not when I print

Or, it could just be that there is a streak on the scanner glass. Anything on the scanner glass will show up on a copy, but not on a print job.

Not sure, but one possibility is that your paper you are copying is not all the way to the edge of the copier. If there is a crack along the edge where light from the room can get in it will show up black in those areas. You will see the same effect if you leave the top of the copier off and try to copy something. There could also be something wrong with the scanner arm preventing it from moving all the way to the edge of the window.