Vertical window are hard to move

A home owner from Thousand Oaks, CA says:
We have aluminum windows in our house. Most of the vertical windows are very tight and in some cases you could see the balance in side rail. Additionally some of windows are cocky when you try to move. I picked a window which was relatively straight but tight, and spray WD40 in the guide. That window got much better but only problem I am seeing is if you move that window at fully closed position at normal rate of motion you can't lock the window. You have to lightly slam the window before you could lock it. what could be the solution. How would I know if the balance are good or bad? My house was built in 2001.
User submitted photos of a window balance.
Profile picture of Tom
Tom from SWISCO responded:
Hey, thanks for posting. I've narrowed this down to two possible channel balance Series: either our Series 351 or our Series 390 balances.

Now, as you can see, there is only one difference between these two Series, and that is their bottom shoe. The Series 351 uses the 15-002 while the Series 390 uses the 15-001. I can't quite tell what you have based on your pictures, though. Please carefully compare their dimensions to your own hardware and see which is a better match.
Alternate view of 15-002
A quick learner from Thousand Oaks, CA says:
You didn't answer, if we replace balance would that take care of window closing issue without slamming it? Is this due to bad balance? Also will balance replacement smooth the operation?
Profile picture of Tom
Tom from SWISCO responded:
I'm sorry. Yes, if your window is slamming shut then the balances are likely worn out and need to be replaced. New balances will make the window operation a lot smoother.
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