Andersen 531 Window Sash Balancer

A quick learner from Stafford, VA says:

I have replaced (left and right) Andersen Window Sash Balancers ("527" stamped on them - see pic) with 531 on my double hung (non-tilting) Andersen wood frame window (bottom sash glass dimensions approx. 16-7/16" wide x 24" high). After installing the new 531 balancers, the top sash operates normally. However, the bottom sash, when opened fully, sags to about half open. Both cords connected to the bottom sash seem to have tension, but apparently not enough to keep window open.

Is the "531" the correct replacement for the original (5/89) "527" balancers, or is it possible that both the "531" replacement ones are faulty??

For my window glass size, the Andersen window website has #531 (non-tempered glass) and #737 (tempered) as the appropriate balancers. I don't think my window glass is tempered glass, based on how one cracked a couple of years ago. But wonder if I should try the #737 to keep my window open.

Thank you for your help/advice and very nice website.

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Tom from SWISCO responded:

Thanks for posting, James. Based on your old stamp of 527, you want the 24-531 Andersen sash balance. I'm not sure why it didn't work for you. It could have been defective, but that's hard to gauge. Did the window get new glass at any point? If so, that could have drastically affected its weight, pushing it past the maximum threshold that the 24-531 can carry.

A quick learner from Stafford, VA says:
Hi Tom,

Thanks for your reply. I don't know if the window received any glass over its 30 years (we've been there the last 19 years though and have not installed any new glass in it). Any suggestion of sash balance though that may have higher threshold than the 24-531 for that window size? I doubt the new 531's I just installed were both defective, but like you say, no way for me to really tell if they have the correct tension.

Thanks again.

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Paul from SWISCO responded:

In my opinion, if the 24-531 is too light for the sash, you should try the 24-637. The 24-737 might be too strong. Keep in mind that I cannot guarantee it will work, but without more data that is my best guess.

A quick learner from Stafford, VA says:
o.k. may give the 637 a try. understand that you cannot give guarantee on it though. Thanks for all the help. Will let you know how it goes (or doesn't).

A quick learner from Stafford, VA says:
I ordered two of the "637"'s from your company and received this morning. I installed them and the window sash now seems to be operating correctly. thanks for the suggestion of these balancers.
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