Sometimes it blows cold, sometimes it doesnt.

The coils that are located right behind the filter need to be cleaned extremely well. You can purchase a spray from your local hardware dealer that can clean the coils. Also, rinse the fins at the back side of the unit as well. Dirty units can cause this to happen. If you clean it and it continues, you have developed a refrigerant leak. Since window units are so inexpensive today, it is not cost effective to hire someone to come out and find and repair it. Hope this is of help to you.