Top window won't stay up

It sounds like the balance has lost some of its tension. I recommend looking at the guide below, this will tell you what you can do to get that tension back.

Oh, I see. Yes, the top sash should also have its own spiral balance. It might be the same as the bottom sash, but this is not always the case. I would see if you have an identical window elsewhere in the house that you can use as a reference.

Yep, spiral balances are pretty easy to replace. You can see our entire selection here. It's important to keep in mind that the supper and lower sash may use different sizes and strengths. If you have an identical window in the house, it'd be a good idea to look over the balances to confirm.