BSI balance, mid 1980s

A home owner from Texas says:
All windows in my house have the same balances. They are all double-hung wood sash windows. The house was built in 1986. There are no four-digit codes on the balance, only "B.S.I." and a two-digit number (on this window, "28", other windows have the numbers "20" or "36"). What type of balance is this? Can it be replaced? How do I remove the sash? Thank you!
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Emily from SWISCO responded:


It looks like you may have a tilt window channel balance but I can't tell what you need from these pictures alone. Can you remove an undamaged balance with the end fittings intact and show us some pictures? I've attached some videos below that you might find helpful. Take a look and let me know if you have any questions. 

A home owner from Texas says:
Hi, thank you for the response. The first think I'd like to know is how I can remove the sashes from the frame. It's an all-wood window, and I can't find anything that looks like tilt latches, neither on top of the lower sash nor at the bottom. The sash side profile is snug with the jamb liner (as shown on one of the pictures), and I hesitate to apply force to pull the sash out of the jamb liner. Or is that what I need to do to remove the sash?

I watched the three videos. The balance and jamb liner in the "How to replace a tilt-window channel balance" video look similar to what I have. If I push the lower sash as far up as possible (after removing the sash stops and the sash lock), I can barely see (looking up into the channel, from the bottom of the lower sash) what looks like the shoe of the balance, inside the channel.

It looks like once the sashes are removed, I can tear off wooden trim on the inside of the window frame, and then I can uninstall the jamb liners and check the balances.

I can take more pictures if you tell me what parts of the window or frame may be informative. Thanks for your help!
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Paul from SWISCO responded:

For these balances, you will need our Series 751 ribbed channel balance with the 15-014 knife shoe attached.

For the balance stamped "20 BSI", see our S751-21 with  a 20R spring strength option. 

For the balance stamped "28", see our S751-29 with a 28R spring strength option. 

For the balance stamped "36", see our S751-37 with a 36R stamp option. The short S-clip is the 15-029 and the long S-clip is the 19-030 .

Before you remove the wood trim, try this. Raise and grab the bottom sash and pull the sash top out towards you from the jamb liner (like a tilt window). The vinyl jamb liners usually have some type of spring mechanism pressing against the wood sash. Twist the sash to unhook the pivot bars from the knife shoes and then repeat the process with the top sash. With the sashes out, cut away any paint from the wood trim and vinyl jamb liner. Now you should be able to remove the vinyl jamb liner from the window frame. Lay the jamb liner down and slide the balance from the jamb liner through the top where the S-Clip is. To install the new balance, hook the S-Clip on the top rivet of the balance. Slide the knife shoe, the 15-014 , first in the jamb liner with the balance and hook the clip at the top of the jamb liner. With a flat tip screw driver, press down the metal knife to loosen the shoe about 12" and lock it in the track. Repeat for the other side. 

You will notice the bottom sash balances use the long S-Clip, our 19-030 , and the top sash balances uses the short S-Clip, our 19-029 . Place the jamb liner in the wood frame and install the top sash first by twisting the bottom to attach the sash pivot pins to the knife shoes. Swing the sash up into the jamb liners and raise it just about three inches short from the top. Now install the bottom sash in the same matter. Now you can fully raise the top sash and fully lower the bottom sash.

A home owner from Texas says:
I just followed your instructions and managed to tilt out the lower sash of one window. With your other instructions, I will be able to check and replace the malfunctioning balances. Thank you!
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