Return Visit - Client mentioned that Dining Room PTAC system wasn’t cooling a few hours after I left. Checked system noticed that this is the same PTAC Unit with traces of oil residue. Noticed that system is low on pressure and while unit is running in cooling pressure is dropping. Informed client when I was here this morning that system had oil residue and the unit is potentially leaking. Evaporator temp very low. Explained to client we will have to return to trace leak and/or add refrigerant. Client mentionted that he is going on vacation and work will have to be done at a later date. Client wants to repair issue. Will have the office contact client regarding return visit to Leak Search and/or Add Refrigerant 410A. Reviewed work with client, emailed invoice.