I was called to repair a heating and air conditioning system in a residential home in Philadelphia, PA 19116. Upon arrival, I found that the system was not functioning properly. I diagnosed the issue as a faulty thermostat and replaced it with a new one. I also checked the air filters and found that they were dirty, so I cleaned them and replaced them with new ones. Finally, I tested the system to ensure that it was working properly. The homeowner was very pleased with the service and thanked me for my help.