I was tasked with the job of AC maintenance and repair for a large commercial building in downtown Phoenix. The building's AC system was over 20 years old and was starting to show its age. I worked with the building's management to develop a maintenance plan that would keep the system running smoothly and efficiently. I performed regular maintenance tasks such as cleaning and adjusting the filters, checking the refrigerant levels, and repairing any leaks or damage. I also performed emergency repairs when the system broke down. I was able to identify and repair several issues that were causing the system to fail, including a faulty compressor, a broken fan motor, and a clogged condensate drain. I also replaced the old refrigerant with a new, more efficient type, which helped to improve the system's energy efficiency. In addition to the maintenance work, I also provided training to the building's staff on how to operate and maintain the AC system. This helped to ensure that the system