If a window air conditioner no longer provides chilled air, the problem is not one that can be fixed with simple do-it-yourself methods. Experts agree that refrigerant leaks should be detected and remedied only by someone who is trained in A/C repair.
Unlike car air conditioners that require periodic “topping off” of Freon or other refrigerant gases, window A/C units are sealed systems that don't readily allow refrigerant gases to escape.
A typical window air conditioner comprises many moving parts along with filters, compressors, coils and sealed refrigerant tubes. Few, if any, parts in a window air conditioning unit can be repaired or replaced by a weekend handyman. If a window unit is not functioning properly, the best bet is to call an HVAC professional.