Performed cooling maintenance on one straight cool system. Checked all electrical, mechanical and performance of the system. Customers replaced the filters recently and they are still clean. The drain line runs into a restroom sink upstairs and was very clogged. I cleared the drain line a few times and tested it with 2 gallons of water and confirmed water is not backing up anymore. I also found that the high voltage wire nuts were undersized at the furnace. I replaced them with the correct size to prevent any electrical shorts. I cycled the system at the thermostat and found no other major issues. The system is operational at this time.