You need to determine the cause for the part not working.
I had a similar problem with my Kenmore canister. I took it apart and found that by 1) cleaning it 2) lubricating it and 3) increasing the tension (essentially) by winding the cord one or more two times, it worked. It has been working fine now for over a year. My cleaner (which Sears no longer seems to want to support with parts) has worked (under light usage) for over 23 years. Oh, the cleaning of the part seemed to be the most important ingredient to getting the cord retractor to work. Together, lubrication and a small amount of additional tension seemed to equal the cleaning step. Oh (#2), be careful as to what you use to clean the retractor and that it is quite dry before you put it back together. I think I used another vacuum cleaner to ensure that the innards were completely dry.
Wayne
August 2007