Performed semiannual maintenance on one straight cool AC system. Inspected all performance, mechanical and safety systems. I lowered the blower speed to match the 3 ton AC system to ensure proper heat and humidity removal. This also helped lower the static pressure of the blower to .40inWC, which is now within range for manufacturer specifications for operation. Homeowner installed a new AprilAire 213 air filter prior to us coming out. The old one she showed me appears to not have been changed out in at least a year. Verified everything was operating within manufacturer specifications for operation. Everything is working at this time.