Checked all operations in the heating and cooling modes. Checked all electrical components and checked the heat exchanger. Upon our inspection we found that there is a crack in the heat exchanger. Due to the crack in the heat exchanger the furnace is unsafe to operate in the heating mode. The furnace is twenty-six years old and due to the age of the furnace we would not be able to replace the heat exchanger since the parts are no longer manufactured this leaves replacement to be the only option. Checked all electrical and refrigerant components at the outdoor unit. Found that the capacitor at the outdoor unit had failed. The outdoor unit is twenty years old and uses a refrigerant that is no longer manufactured. The customer is going to get a bid on replacement before deciding to make repairs.