Window counterbalance

A quick learner from Oceanside, CA says:
May 14, 2018
Hello,

I need to replace a broken window counterbalance. Narrowed it down to S395-27. I weighted the sash and it is 23lb so I was going to purchase 2640.

The original has markings (see attached) 26-6 FA2 CMC 13 and am unsure if that is suggesting 2660 as the replacement. The window was difficult to pull down to close but unsure if that was due to the counterbalance being worn (and ultimately the string snapped) or if it was the wrong part for a heavier window.

Should I go with the 2640?
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Tom from SWISCO responded:
May 18, 2018

If your sash is exactly 23 pounds, then the 2640 option would be best for you. Your old stamp, 26-6, indicates a spring that can carry 30 through 33 pounds. This is way too strong for yours ash weight. Was your window always hard to close, or was that a more recent issue? If it was always hard to close, that would account for why.

If I were you, I'd go with the 2640 option. It's possible whoever installed your balances just put in whatever, or even erroneously thought that stronger = better. The sash weight doesn't like, though. 
A quick learner from Oceanside says:
May 25, 2018
The windows were always hard to close since I bought the house 2 years ago. The 2640's arrived and I put them in. They work much better and the windows are easier to close.

Thanks for your help!
27" Series 395 Channel Balance
27" Series 395 Channel Balance
S395-27
$10.23
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