Congratulations on becoming an Electrolux Model G owner!
Keep in mind that the spring and latching mechanism of an Electrolux USA (now Aerus) cord winder is similar to a roller shade.
When a roller shade loses its tension one needs only to extend it to the length of the window and allow it to latch, remove it from the left bracket, roll it up several inches at a time by hand; remounting it to the bracket afterward and testing it until obtaining the desired tension.
Similarly, for a cord winder, one needs to extend it several feet until it latches, remove its cover, and wind the cord several turns manually at a time in order to achieve the correct tension (just enough for the cord to gently retract the entire way). By the way, an old salesmen's tip is to dust the cord with talcum powder to help facilitate proper extension and retraction.
In either case, it is advisable to guide the object (shade or cord) with one's hand and not just allow it to retract on its own to avoid possible damage.
Best wishes. Let us know how it turns out (excuse the pun).