Called out today to perform a precision tune up on both units. Checked all electronics and motor components to ensure equipment is operating properly within manufacture specifications. Checked and cleaned filters. Tested safety switches on the central air unit (in the attic) and found that neither switch responded. Checked to ensure wiring was correct. Recommended replacing both float switches to ensure no water damage occurs. Cleared drain lines with solvent followed by a gallon of water. Outside I removed the fan from the condensers and cleaned the coils from the inside out. Vacuumed drain line clear from outside port. The contactor located on the main units condenser is failing. The coil on the contactor is pitted and buzzing when energized. I also recommended a drain solve treatment for both drain lines considering how filthy both units were. Drain solve is a harsh chemical that breaks down algae build up within drain lines and allows for proper drainage. Equipment is op