aw 11600-2 replacement

A quick learner from clinton nj says:
I've got to replace a few counter balances. I saw a posting stating that the 419,425,431 would work.
Got those, installed a pair, but no dice. They are too weak to support the window. Do you know the pull strength of the various models or can otherwise direct me towards another model?
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Mike from SWISCO responded:
It appears you're referring to the 24-431 Andersen Sash Balance.

In order to determine the correct replacement, please take a few photos of your current balance and upload them so we can take a look. Please report to us any and all markings found on the balance.
A quick learner from Clinton NJ says:
Markings. On the side where the stops pull..
11600-2. same side other edge, P37 12 26 8 82
turned over...1600-3 US patent # 3,335,455
pat 1967 CAN.
I had purchased 24-431...too weak
window dims(unknown model).
39.5"w x 39.5"h(way too weak)
39.5"w x 27"h (a couple lbs weak)
User submitted photo of Andersen window crank.
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Mike from SWISCO responded:
We believe the 24-1231 Andersen Balance may be what you're looking for.
A quick learner from Clinton NJ says:
ok, i'll try it. you didn't answer the question though. what make 24-1231 the right choice.?
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Donna from SWISCO responded:
The given numbers 12 26 may be the identifier we needed. The 12 would represent the strength and the 26 could indicate the cord length thus making the 24-1231 a good replacement. The newer model balance boxes are a little easier to identify.
A home owner from pittsburgh says:
I have to change a sash balance for some windows (10 windows),one of them have this number F412 31
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Mike from SWISCO responded:
Please take a look at our 24-1231 Andersen Sash Balances and see how it compares to your own.
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