Performed semiannual maintenance on one straight cool AC system. Inspected all performance, mechanical and safety systems. I found that the external static pressure of the furnace was high, reaching over 1.02inWC. I lowered the blower speed to bring the CFM rating down to match the tonnage of the cooling system and was able to lower static pressure to .85inWC. This also helped with proper heat and humidity removal of the system. Did verify refrigerant levels were still within operating range after making changes to fan speed. Tested and verified everything was operating within manufacturer specifications for operation. No major issues were found. Everything is working at this time.