How do I remove my Acorn upper window sash?

Thanks for posting, Mike. You should be able to pull it down and tilt it out. If it will not pull down, then there may be nothing that you can do. In some windows, the top sash is stationary and is not meant to come out. This may be one of those times. You still may be able to replace the glass, though. You would first remove the vinyl glazing snap in that surrounds the glass, and then with our 75-052 tool or a utility knife, you'd cut away the sealant holding glass to frame. Of course you should be very careful. I recommend wearing gloves.