Top window falls automatically

Counterbalance is not working. Could be weights and pulleys, could be the spring things on the sides. Determine what type you have first, then either repair the cords or replace the parts. Could be some newer version too, but you didn't give much to go on.

Thanks. It's a double-hung window - installed 5 years ago. I cannot seem to find the maker - but it looks like the anderson double-hung 200 series. I do not see any "pulley/weight" system. The top window falls on its own as soon as it is unlocked - it is supposed to slide down only upon pulling it down. I do not actually see any mechanical system after it slides down (or after pulling down on the top window). Not sure how much more details to provide...

There seems to be a recall on the latch for that series:

The 200 is a "tilt out for cleaning" window. You are not going to find a cord.

Learn something new everyday. I thought the 400 was the tilt and the 200 the narrowline???

Here is another link to the notice of problems with the series 200:

Andersen® 200 Series Tilt-Wash Double-Hung Window

There are even pictures. No cord.

I have the same irritating problem with mine. Open the bottom window and the top window falls down open also.