To add to Ranger's suggestions, you should probably have a helper in the car. After you have cleared the ACM codes (do this with the Climate Control or "CC" off), have your helper bring up the revs to 1500. You are at the fill port connected with the freon (now bled of air) fill tube ready with the release valve. Have the helper turn on the CC (just touch the AUTO button). Now you have about a minute to recharge the refrigerant. If there isn't a serious leak, the "Low refrigerant" message should not re-appear.