Removing the cable from the chair arm rest?

I am moving a mdl 420 stair lift( lift is about 5 years old) from one house to another house. The lift will be installed on a basement stairway however, it will not go down the stairway do limited clearance. The lift can pas through the basement window with the seat removed. I do not have a manual for the lift. How do I disconnect the cable from the chair arm resr? I do not want to do something that will damage this lift.