Furnace clean and tune. Cycled system. Checked heat exchanger, ok. Checked, removed, and cleaned burners and flame sensor. Burners and flame sensor were both worn and corroded. Cleaned as best as I could. Checked and adjusted gas pressures to maximize efficiency. System was out on pressure switch fault. Checked and cleared drain lines. No blockage found. Ventor motor causing water to build up in tube port to pressure switch. Due to this, ventor motor was replaced. Preformed combustion test and found normal levels found in exhaust. No CO found in airstream. System operating normal at this time. Job complete.