No ac call on Lennox attic style system consisting of a Lennox horizontal right gas furnace, CH style evaporator coil and condenser. Homeowner replaced MERV 11-20x25x5 style filter with a 20x20x5. Homeowner reported system “struggling” during the high heat/humidity from the previous weekend. Troubleshooting found a faulty water sensor in the overflow pan. Discovered a short in outdoor low voltage wire as well. Was able to use different conductors to get the unit running again. After finally getting the system up and running found low refrigerant charge. Added easyseal and (4) lbs R-410a refrigerant. Completed maintenance. System operating properly at this time.