It could be that you're window ac is freezing up due to having dirty coils. Check the coils "the radiator fins" both back and front and make sure the fins are clean and not bent.
These coils must be clean for air to pass through them and work properly.
If it's not that then it could be low or out of freon r12 refrigerant and if it is then it's ready to go the recycler and head to the store for a new one.