block and tackle channel balance

A quick learner from Brooklyn, NY says:
I just replaced both block and tackle channel balances in my aluminum window. The old balance was stamped 3040W and I replaced both with ones that are stamped 3040.

Now my window is very difficult to move up and down. It feels like there is too much tension in the block and tackle channel balances.

Does anyone know what might be causing this? I am tempted to install new balances marked 3030. Is this advisable or are there any suggestions to correcting this issue?
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Tom from SWISCO responded:
Thanks for posting! It definitely sounds like the tension in the balances is too high. However, before we try out any other stamp, we should know for sure what you need. The only way to do that is to weigh your window sash.

Also, what Series balance do you have? I assume it's 31", based on that stamp. Is that correct? If you let me know that information, as well as the sash weight, I should be able to tell you what option you need.
A quick learner from Brooklyn says:
Hi Tom,

Thank you for getting back to me so promptly. The balance is Series 351 and it is 31" long. The weight of the sash is 27 lbs. The 3040 looks like the correct stamp but the window is very hard to move. What would happen if I use a lower stamp? I really appreciate your help.
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Paul from SWISCO responded:
I've been giving this some thought and I have a few ideas. First, compare the depth of shoe on the new and old balance. Are they the same, or is the new one deeper? If they are the same then check the window track to see if there is a kink on track or even in the sash itself.

Also, if possible, do you have the same size window with undamaged old balances? If so, use those balances in the problem window and see if they work. That will let you know if it's even the balances that are the problem at all. If all else fails, you can consider going down in weight rating and use a lower option. It's not recommended but it may be the last recourse.
A quick learner from Brooklyn, NY says:
Hi Paul,

You make a couple of excellent suggestions. I have checked the old balances and they are the same depth as the new ones. I also switched the balances from a good working window of the same size and the problem still existed. Then I pried the frame a little to create more gap for the sash. Before putting the sash back in I lubricated well with lithium grease. The window is now moving a tad bit easier but still feels very tight. When I close the window completely the top sash comes down a little and I then have to use a crowbar to push the top window up in order to lock it. These seem like good quality (steel) windows but I would love to be able to open and close them without this much effort. Thank you!
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Paul from SWISCO responded:
Ah, I see. In that case, I think your only recourse is to drop down to the 3030 option. I can't guarantee it will work, but I honestly can't think of anything else.
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