Pull one of the sash cords until the sash weight hits the pulley then lower the weight about 3 inches.
Sash window weights stuck.
Replace the access doors to conceal the sash weights.
Prying off the window trim may or may not give you access to the weights but you won t know.
For a window without access panels you also need to remove the window casing.
Sash cord snapped if your sash cord snapped and the sash has twisted in the frame becoming stuck firmly then you are in luck this is the easiest fix.
Feed a new length of sash cord over the pulley on each side jamb and down into the wall cavity.
Remove the window and then open the panel cover on the side jambs to access the sash cord weight and pulley.
Access the window sash cords.
Set the sash partially into the window opening.
Pry the old sash cords from the sides of the window sash.
Windows old enough to have sash weights have probably seen a variety of painters of various skill.