Arrived at the home to provide AC Repair & Service. Upon arrival customer said to her knowledge system was working properly. Talked to customer about the things I will be taking a look at today. While doing tune up I discovered system was a 26 year old Rheem system. System has a crack in the induce draft motor assembly, rust buildup in heat exchanger, with the crack in the draft motor assembly and rust build up in the heat exchanger system is putting off carbon monoxide into attic which is a health hazard. single wall flue elbow going to double wall pipe thru the roof. Also found system with dirty blower wheel with dirty blower wheel the system is unable to move adequate air thru system.(unable to pull to clean due to truss blocking it). Condenser also has condenser fan motor and shield from a different unit installed on it. Went over everything with customer and made her aware of the concerns we had with the system. Also gave pricing and options with the customer.