In a chemical wash, your Tasker cleans the coils, air filters, and water trays. Meanwhile, in a chemical overhaul, the Tasker also cleans the drainage pipes, heat exchange coils, and blower wheels. They’ll also inspect the entire unit and repair anything that needs fixing. In short, a chemical overhaul is (usually) a two-in-one job that involves cleaning and repair. This kind of service should ideally be done by a technician once a year or as stated on your contract.