I have replacement windows throughout my house. They are 20 years old & all the spring balances ceased functioning.
How do I repair them? Where can I get the tool required to rewind them?
It is generally pretty easy to replace spring balances, usually a matter of removing a couple screws. When they quit working it's usually because the spring has broken, there is no repair, only replacement.
Look for a manufacturer's tag on the windows as a clue to source replacement parts. :)