Fiberlux window parts

A home owner from Fanwood, NJ says:
We bought a home recently. All windows in the den - 4 in number - have their bottom sashes not staying up at all: That is if they are lifted up, they fall with a bang offering no resistance at all to stay up. These are tilt windows.
It seems strange that all 4 windows in the den have this problem - it looks like something was not fixed right on purpose. The top sash of all of these windows stays up though without a problem.

I could see that there is a name - Fiberlux - written on the sash in tiny letters but nothing other than that. The sashes are very heavy and appear to be made of metal. Each sash weighs about 11 pounds 11 ounce. The spiral balance measures 17".

I'm not sure what the problem could be. I looked at the videos on this website and attempted tightening the spiral balance by turning it clockwise 2 rounds each time, but it makes no difference at all. What should I be replacing - the spiral balance or the shoe or could I fix this with some other adjustment? I know that the spiral balance is not completely bad because when I tilt the sash to take it out, the spiral balance holds it in place about half the way firmly and without dropping it (my last picture shows this). However when I make the sash straight again it just drops like a dead weight.

Appreciate any help with fixing this and also a link to a guide showing how to replace the shoe if that is what needs to be replaced.
A customer submitted photo of a spiral balance.
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Paul from SWISCO responded:
From what you've described, it definitely sounds like the spiral balances are the issue. Tell me: when you charged the spiral balance, did you feel any tension? If not, then the springs may be broken, and you will need replacements.

In either event, could you tell me the weight of your window sash? You can find this out by removing it and placing it on a scale--any common bathroom scale will do.

Can you also tell me the diameter and length of the metal tube of your balance? This will help me determine the Series and, in addition to the sash weight, if you have the appropriate balances installed.
A home owner from Fanwood, NJ says:
Hello,
When I twist the spiral balance, there is some tension for the first twist and then some more tension for the second twist.

The weight of the sash is 11 pounds and 11 ounce.
The diameter of the tube is 5/8" and its length is 17 inches.

I will also need weatherstipping for these windows if you are able to figure out which ones they are.

Also, do you allow for in-person pickup (or return just in case) of parts from your store since I am also in NJ?

Thanks for the help,
Harry
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Paul from SWISCO responded:
Thanks for getting back to us. If there is still tension, then I don't think your balances are broken. You might just have to wind them a bit more. Give it another handful of turns and see if that improves things. I would look at our 75-006 tilt window spiral balance charging tool and see if that might make it easier.

As for the weatherstripping, I am not sure what you have for these windows. You would have to remove a sample and take a profile picture of it for me to look at, along with dimensions.
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How to replace a tilt window spiral balance.
Video
How to replace a tilt window spiral bala...