Furnace clean and tune. Cycled system. Checked heat exchanger. Found all chambers are rusted and worn. No visible cracks found at this time. Removed, checked, and cleaned burners and flame sensor. Both were rusted, but ok. Checked electrical connections and clamps. Checked and adjusted gas pressures to maximize efficiency. Checked for levels of XS air and CO in exhaust. Normal l vela found. No CO found in airstream. Ac. Replaced filter. Cycled system. Checked and cleaned electrical compartment. capacitor tested low. Used coil cleaner on condenser coil. Hooked up gauges and tested pressures and temps. Found subcooling was 10, indoor coil temp was 40, indoor temp split was 15. System is worn, but operating normal at this time. Job complete. Office to bill for this job.