Place an alarm on your air conditioning unit. Alarm systems are designed to attach to an AC that are difficult to remove and they emit a high-pitched scream when the unit is tampered with. This helps scare away potential vandals or thieves who want to find an easier target.
Lock a protective cage around your air conditioner. AC cages are designed as anti-theft devices that are difficult to remove or saw through. A thief would not be able to access the copper in your air conditioner without first bypassing the cage and most thieves won't want to risk the added time and effort. This also helps protect the alarm on the system if you installed one.
Light your air conditioner at night. Thieves generally prefer darkness since it helps reduce the chances of being seen and caught. Security lighting will activate either because of a lack of sunlight or because it detects motion and either option will help secure your system.
Install a fence around your property. Ideally the fence should be at least 7 feet high to be more difficult to climb over. This provides another barrier between a thief and your air conditioner, helping reduce the risks of vandalism or damage.