Performed heater tune up. Filter recently changed, temp rise is within specs, amp draws are within specs. Cleaned flame sensor and burners, hot surface igniter is reading 187 ohms, adjusted gas pressures to 3.5 inWC. Flushed drain line, tightened and checked all wires, system is operational at this time. Recommend: Upgrade system for efficiency. Maintain maintenance. Surge protector. Hot surface igniter. Primary control board.