another broken coiled spring

A handy person from Chicago says:
This is my 3rd attempt at contact. My mother's bathroom window again will not stay open. I have replaced the S170-336 coiled spring balances twice. This is the 3rd time. Sash weight is about 10 pounds as I remember. there are no numbers visible. Both coiled springs just broke about the middle. Very unsatisfied with this product. Could I please get some help with this?
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Tom from SWISCO responded:
Thanks for contacting us. Sorry to hear you're having trouble. Usually when the coil springs break like you describe, it's because they are not strong enough to support the sash. Can you confirm the exact weight of the sash? Are you also positive that the Series 170 is the proper replacement balance? If you aren't sure, please show us a picture of the original pivot shoe. That will allow us to determine the proper Series.
A quick learner says:
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Tom from SWISCO responded:
Thanks for getting back to us. I have received your pictures, but I'm afraid you do not show the pivot shoe. That is a key detail in determining what Series balance it is you have. If you can show me the pivot shoe, I can tell you if the Series 170 was correct.

Were you also able to weigh your sash? We will need the exact weight.
A quick learner from Chicago says:
Here are more pics Sash weight is 14.5 lbs. Pretty silly. A number or color code would be a lot easier then me taking that window apart twice just to take a pic. What do customers without internet do, take a 35 mm pic and mail it?
User submitted image of their window hardware.
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Tom from SWISCO responded:
Thanks! Sorry to have you jump through hoops, but this is the only way to be sure. Keep in mind most window manufacturers don't want to make it easy, since they'd rather you just replace the entire window if only one tiny part breaks. We try our best to make sure this isn't necessary, but it does require a bit of homework. My philosophy is that it's better to be safe than to be sorry.

Now that I see your shoe, I can confirm that the Series 170 was correct, but the strength option you purchased (S170-336) was not. Each of these springs can individually only carry 6 pounds, so one on each side carries sashes weighing 12 pounds. Your sash is too heavy at 14.5 pounds, which explains why your springs have broken over time. They may work slightly at first, but as the years go by the strain is too much for them to continue to work properly.

With that in mind, I recommend our S170-407. Two of these can carry 14 pounds, which is only half a pound less than your sash. I don't think that will make too much of a difference. Another way to confirm is to look on your old springs (if you still have them) and refer to the number printed on the coil. That's usually the best way to determine what you need.
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