Performed annual maintenance on air conditioning system. In second floor evaporator coil cleared drain lines, tested blower capacitor which tested normal, changed return air filter 20x24x1. Cleaned inside coil does show small signs of mold spores. Took a temperature difference and was only getting a five degree difference. Outside at condenser unit not running noticed heavy burn marks on contactor and disconnect box one of the line wires burnt and not connected. Disconnect box needed to be replaced and contactor before I could test unit. Hooked my gauges up and noticed system was low on refrigerant. Charged system took a temperature difference again and it was at 16.