poor window operation

There is a catch on each side of the upper window sash that prevents either window from opening more than about 4" (shown in the second picture). Can I get replacements for these?
The upper sash drops as soon as the locks are released. What mechanism supports the upper sash to make it stay in place (and how do I replace it if it needs to be replaced)?



Hey there,
Thanks for reaching out! I am confident we can supply you with a replacement for your existing Alumax sweep lock but I'll need a bit more information to determine the correct one. To start, I'll need to know the measurements for the distance between the installation holes (center to center) and the the backset (center of hole to the back of the sweep lock). Take a look at the diagram below for reference.

In regard to the catch on each side of the window, I believe you may be referring to the window vent latch. To determine the right replacement, I'll need to see a clear photo of the part. Unfortunately, its a bit difficult to identify the exact replacement from the photo provided.
The issue with the upper sash sounds like it could be attributed to missing or damaged balances. This is what is typically used to support the sash weight and prevent it from slamming down. If the balances are still in the window channel, I'll need to see one or both of them removed to identify the correct replacement. However, if the balances are missing, I'll need to see a balance from a similar window in the home. There will also be a few other details I'll need but I can only determine what they would be once we identify the balances you need.
Please feel free to reach out with any questions you have in the meantime.

The problem with the balance springs was they had become detached from the window sash. I got them re-engaged and they are working for now. I am attaching a picture of that mechanism for possible later reference.
All I think I need now is some of the vent latches. I have attached a picture of it in the window and of the part itself. The slot it snaps into is 1/4" x 1-7/8".



The vent latch you have here looks a lot like the 26-122 Vent Latch. Carefully compare the dimensions to confirm that this is the right fit.



The balances you have in the window are a tilt window spiral balance. To identify exact balances you have, there will be a few details you'll need to gather. The video below gives an explanation on the information you'll need.