Arrived on site for heating maintenance. Customer said you knew was no longer turning on after attempting to change filter. Closed unit up and started up the unit everything was fine. Ran a combustion test, Co levels were 40 to 45ppm. The manifold and intake of the gas valve access was stripped, could not check the gas pressure from the manifold side. Removed the flame sensor, cleaned flame sensor and reinstalled the flame sensor. Checked microamps of flame sensor, reading was 0.1 to 0.7. Inform the customer about the flame sensor and recommended a replacement, customer said they rather wait.
