I have old wooden frame sash windows with weights inside the walls beside the windows. However, The ropes attached to the window and the counter-weights had become worn, some even had broken, so I had the old ropes replaced. The guy that did the repair used much thinner rope than was there before. Before the service, I could raise the lower window to any height and it would just stay there. Now, the window won't do this, if I unlock the window, the lower sash just flies up all the way. It's like there is no resistance. Added to this, the window won't stay shut unless I lock it in place. If I don't lock it, it will just shoot up. When I asked the service guy about it, he said that the way it's supposed to be. Is he correct or just covering for a bad repair job? Can anything be done now to restore it to its former function?

If he didn't touch the weights/counter-weights and the "rope" wasn't the same gauge or was a lighter weight rope, he threw off the balance and counter balance weights. If he did attempt to adjust the weights/counter weights to fit the new rope gauge, he did not adjust them correctly. It sounds as if he is limited in his experience in dealing with windows such as yours and he never should have taken on the job.

Unfortunately, the original parts for older windows like the ones you have are hard to come by and the people who know how to find a good substitute to fix them so they will function correctly are few and far between. Usually your best bet is to find a hobbiest or professional antique restorer. Both do it for the love of the challenge and/or simply the love of working with anything antique. Call your local chamber of commerce and see if there are any antique home restoration businesses in your area. If there isn't anyone, see if there is any business that specializes in general antique restorations. If any of those people can't help you directly, they might know someone who can.

The weights used in your type window are of different sizes(weights). The heavier weight is used on the upper window and the lighter on bottom.

It appears that the weights where reversed.

If u open up to fix this, I would change cord to sash chains as these will not wear out. The chains come in a bag/package that have the necessary clips and springs to do install. Will probably have to go to a hardware store to get the chain.

Chuck