Coil balance replacement

A quick learner from United States says:

I just received my order (1216158) for parts for a double hung vinyl window that doesn't stay in the open position.

I purchased a set of 15-186 coil balance clips, 15-180 coil balance shoes, S190-840 coil balance springs (8 stamped on them), 15-182 balance bushings and 33-073 trus head screws.

I replaced the old parts with the new ones with no difficulty. However, the window still does not stay in the open position. The condition is not ant worse or better with the new parts.

Do you have any suggestions?

Could I use a stronger spring (the old spring has an 8 stamped on it just like the new ones)

The window sash goes up and down smoothly but I am wondering if the window track is out of whack and not allowing the shoe to grab hold. It looks ok to me.

Any ideas or suggestions would be greatly appreciated.

Thank you,

Michael

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Tom from SWISCO responded:

It definitely sounds like your springs are too weak. Since your old springs were also marked for 8 pounds of support each, it's possible that you never had the right springs in your window. Can you tell me the exact weight of your sash? That will tell us for sure one way or the other. If it is 16 pounds then we can at least eliminate spring strength as the culprit and look into other possibilities. 

A home owner from United States says:
Tom,

I weighed the sash and to my surprise it weighed 25 pounds. It must have been manufactured that way. We are the original homeowners and all the windows were installed when the home was built and this is the only one that is not working right. My wife said that this window has been like that for as long as she can remember.
I would assume that I need different springs? Can you tell me which ones I will need?

Thank you

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Tom from SWISCO responded:

Aha, I suspected this may be the case. Thanks for doing the legwork for me. We can definitely get something to work, but since this sash is extra heavy we'll have to double up on springs. 25 is an odd number, though, which means we'll have to fudge the numbers a bit.

You have two options ahead of you: you can go for 24 pounds of support or you can go for 26 pounds of support. I think either should work fine but it's ultimately up to you if you want to go a little weak or a little strong.

If you want to go for 24 pounds, you can use two S190-640 springs on each side (four altogether). If you want go go for 26 pounds, you'd use one S190-640 and one S190-740 springs on each side (two of each).

You'll also want a 15-181 double spring clip and a second 15-182 bushing for each side. You should be able to slip the larger coil system into the old cutout if you snake it in, but I've had some customers tell me that they had to make the cutout bigger by a little bit in order to fit it all. You may need to do the same, but try to install as-is first.

Let me know if you have any questions!

A home owner from United States says:
Tom,

Since I am going to be using a double detent clip, do I need to use two screws to attach the assembly to the window track?
If so, to you sell the screws, I don't see them on your site?
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Tom from SWISCO responded:

Yes, you'll want two screws. I recommend taking the old screw to a local hardware store and having them match up the size. 

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