Customer stated the downstairs system was not cooling. I evaluated system and discovered the out door condenser coil had a refrigerant leak in it. I was able to locate the leak. Customer approved for the repairs to be done on her system. I recovered and disposal of the refrigerant properly. I had to repair the copper to aluminum joint and make copper modifications to properly repair leak. I nitrogen tested and pulled a 500 micron vacuum and recharge the system with new R410a refrigerant. I charged the system to manufacture specs and tested operations everything is working properly at this time.