Arrived on site to perform furnace diagnostic on 1999 comfortmaker heater. Upon arrival Casey stated that Upstairs system is not heating and they like to run it at 78°. Began diagnostic at furnace And immediately found that the system had overheated and is in cool down mode to prevent any further damage from melting or catching fire. Inspected condition of motor and electrical and found that indoor blower motor is leaking a significant amount of oil. The biggest red flag found was that the heat exchanger is cracked on both chambers indicating that the furnace has been overheating for a long period of time resulting in failure of this main component. This is not a major safety concern for everyone in the home while the system is heating due to the possibility of combustion gases entering the airstream during operation. Furnace should not be ran under these conditions unless the Heat exchanger is replaced or Looking into long-term options. Ultimately Casey is aware of current failure po