Balance string loose on single hung aluminum window

Hi,

The string became detached from the balance spring on one side of this single hung aluminum window, and I wonder if you carry this part.

The first photo is hard to see but shows the full length of the square channel, with the string at the bottom and a fastening screw at the top. The string attaches to the bottom of the sash. The second image shows a close-up of the top of the channel and the 3rd shows the bottom with the string coming out.

Can you identify this part?

Thanks,
Dennis

Additional info: I took the balance channel off and photographed it from the inside. Please see attached photos.

Is this something you carry?

Would the color match the window color?

Thanks,
Dennis

And I see a stamp on the balance channel: J C2830.

Does that help?

Thanks Paul! The sash weight does work out to be a C stamp. I've now ordered a pair of these.

Best,
Dennis

I have received and installed the S770-29C window balances. They went in fine, but while the window now slides up quite easily, it is somewhat hard to pull down and close.

It turned out my sash weight was 18.5 lbs, so I opted for the C stamp option instead of B, but since I'm at the very low end of the C range, I assume that is why it's easy to open and hard to close.

Can these channel balances be adjusted at all for a situation like mine?

Thanks,
Dennis

I posted the message below a few days ago, but since I no longer see it in this discussion thread, I thought it might have gotten lost, so I'm resending it.

I received and installed the recommended channel balances. However, while the window is very easy to raise, it is somewhat difficult to lower. This is probably due to the fact that the sash weighs only 18.5 lbs, and the C stamp that I ordered is for 18-23 lbs. Probably a sash of 20-21 lbs would have been equally easy to raise and lower.

So I was wondering if there's a way to adjust this channel balance to accommodate situations like mine. I would need to either reduce the spring tension or increase the mechanical advantage of the pulley system.

Thanks,
Dennis