Hi there!
Thanks for reaching out to us. The 15-228 may be what you need. This pivot shoe is designed to use the 1/2" S160 and 3/8" S165 coil springs. The video below will show you how to remove your hardware by making a cut out in the window track.
Did you ever have trouble closing or opening this window? I ask because the old coil spring support is stamped "9.0LB". I'm assuming the support on the other side of the window is stamped with the same. That would mean the coil balances total 18 pounds of support which is too strong.
If the window weighs 13 pounds and the spring band is 1/2" wide, you can use one S160-06 6.5-pound spring on each side of the window. This totals 13 pounds of overall support.
If the window weighs 13 pounds and the spring band is 3/8" wide, you can use one S165-7 7-pound spring on each side of the window. This totals 14 pounds of overall support which should be fine so long as the coil weights total within a pound of the sash's actual weight.
