Channel balance can't support sash weight

A quick learner from Santa Clara, CA says:
July 18, 2016
I received and installed this window channel (S 385-32, opt 3130 )balance but found it's not strong enough to support my window (window cannot stay fully open by itself). My window weights 44 lbs so I chose the 3130 option since the sash weight range is 16-23 lbs but it appears I need a stronger pair. Also the window balance makes a lot of noise during open and close. Could you provide a recommended weight option for my case?
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Tom from SWISCO responded:
July 20, 2016
Sorry to hear about the trouble. It sounds like you divided the sash weight in half to determine your option, which is not the proper method. Our weight range chart is designed with both balances in mind. The balances you ordered are two weak by half.

44 pounds is actually a pretty heavy sash. You may need your balances to be custom made. Can you tell me what the stamp on your old balance read? Can you also tell me how many balance you would need?
A quick learner from Santa Clara says:
July 20, 2016
Attached is a photo my old balance and it appears the stamp reads "31 9". Each 44 lbs window has two balances on each side. Could you provide a quote for 1 and 3 pairs of the custom made balances?
User submitted a photo of a window balance.
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Tom from SWISCO responded:
July 26, 2016
Thank you for posting, could you take a photo of the spring so we can help identify the proper part?
A quick learner from Santa Clara says:
July 27, 2016
Attached are two photos of my old window balance. Let me know if any additional information is needed.

Besides, it looks like my window can stay half open with the 3130 balance. I'm wondering if a regular stronger balance, say option 3150, can do the job instead of a custom made one?
User submitted photos of a window balance.
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Paul from SWISCO responded:
August 2, 2016
Ah, I see the problem right away. You do not have the Series 385 balance. You have a unique type that needs to be custom made. It's actually not compatible with any of our standard balances at all. This explains all the issues you've been having.

Can you confirm the length of the metal channel? It should be 31-5/8". Can you also tell me how many you need? Once I know that I can send you a custom order form with a price quote.
32" Series 385 Channel Balance
32" Series 385 Channel Balance
S385-32
$11.52
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