Performed a three system tune up checking cooling. Checked all inside units electrical and mechanical components, amp draws, capacitors, filters and drains all looked good. Then checked outdoor units pressures amp draws and capacitors. Found pressures to be good and amp draws good. Did find that the capacitor for the upstairs unit had a burnt start wire for the compressor and it also melted capacitor terminal. With approval replaced capacitor and made wire repair. System is now cooling properly.