Central ac unit

If it is a central air unit and disconnected (nothing hooked up to the copper lines from the unit), it will be most likely be drained. There are schraeder valves that should be there near or under a brass cap. Similar to a valve stem on a car, if there is no core in there, there is no pressure. I am not condoning releasing refrigerant into the atmosphere. The right way is to hook up a set of refrigerant gauges up and see if there is pressure.

After that is taken care of, there is a fan, compressor, copper lines, and a coil to scrap, you will get better money by taking the ends off of the coils if there is any steel. Just be wary of the oil in the compressor that can dump out and some yards prefer to have them sealed off/oil drained.

Ive had central a/c units disconnected from the house that were still charged with refrigerant. I would say to check the brass filler stem that looks like a valve stem from a tire. Press the button and see if theres any pressure in it still.

Just hope that he didnt leave behind a aluminum rad a/c. Those are what i usually find at the curb.