need to replace window balance

A home owner from Smyrna, TN says:
I have several windows in a home we recently purchased that need to be repaired. One balance is marked 18C BSI G, the others are 28B BSI G. I can get the balance loose in the channel, but anyway I turn it, it will not fit through the opening. There are no removable parts in the channel. I am attaching pictures of the balance, the foot, and the window sash attachment.

Thanks for the help.
John I.
User submitted photos of their 28B BSI G channel balance system.
Profile picture of Paul
Paul from SWISCO responded:
Good Morning,

You have our series S775-18 (with the 18C option & your shoe size) & S775-28 (with the 28B option & your shoe size) window balances. The tilt bar is our 26-021.

It seems the spring or string is broken in your window channel. The nylon shoe attached to the bottom of the balance has a pin sticking out that locks the sash in place when tilting the sash in. So to remove the broken tilt shoe with balance, stick a large flat head screwdriver into the center of shoe and turn the shoe counterclockwise to release it. Unscrew the balance at the top and you can now remove balance.
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