24 in spiral 9/16 thickness double hung window balance

Thanks for posting. It looks like you might have the S600-24 Spiral Balance. Basically if your balances cannot hold tension, and therefore cannot hold the window up, they should be replaced. With spiral balances you can always try adjusting them to see if they just need to be 're-charged' before replacing them. The guide below explains.

Guide: How to adjust a spiral balance on a tilt window