Original window spiral balance

My original double hung wood window suddenly lost all tension. After taking out the spiral balances to inspect, I noticed one of the blue tips had come apart from the spring. I pushed it back together and reinstalled, and tension is back a little but not 100%. The window slowly slinks closed.
Not sure what I need to replace at this moment, and/or if the problem has to do with some rotting wood where the bottom bracket attaches, and I couldn't for sure identify which series and bottom brackets to go with.
Can you advise every piece I need to remove and reinstall?
Note, the metal tube and spring had been encased in a white plastic tubing, which has aged and cracked off, but you'll see a piece of it in the photos.
Thank you so much!
Ruby



Hi Ruby. Is the outer tube 5/8" in diameter? If so, you likely need a Series 500 Spiral Balance. These are often used to replace older balances on old, non-tilt wood windows. Measure the length of the outer tube, up to and not including the colored tip bearing, to determine the length needed. These balances use the 17-012 Bracket to attach to the bottom of the sash. This blog article here explains how to remove and replace non-tilt spiral balances. Let me know if you have any other questions.

Please see attached photos. The original plastic shell of a tube is 5/8" (it's broken, cracked and so there's just a piece of it in the photo) but the actual metal spring/tube is 3/8". Which is the determining measurement?
And if the length not including blue tip is 23.25, is ordering the 23" okay? Seems so, that a tiny extra length will just extend into the hole of the sash.
Thank you, I'll be able to order halong with the 17-012 brackets as soon as I'm clear.
Best,
Ruby



Bob's not here today but I'll do my best to help.
You don't want to measure the spring. You need to measure the outer tube, as Bob mentioned above, so that would be the nylon sleeve removed from the balance. If that's 5/8" then the Series 500 he recommended is what you want.
As for length, when it comes to spiral balances with a length that doesn't come out to a full inch, I typically round to the closest inch. In your case 23" should be okay. In a worst case scenario you can always redrill the installation screw 1/4" lower in the track to make up the difference. I've done that myself in a pinch.