LED flashes code 34; ignitor glows but burners do not light, or light briefly then go out.

Safety: Turn off gas and power before removing burners or sensors.

• Step 1 – Clean flame sensor: Remove the flame sensor and gently clean with fine steel wool. Reinstall and ensure it is positioned in the burner flame.
• Step 2 – Inspect burners: Remove the burner assembly if accessible. Clean burner ports with a soft brush and compressed air. Do not enlarge the ports. Reinstall securely.
• Step 3 – Check ground connections: Verify that the burner rack and gas manifold are tightly fastened to the furnace chassis. Clean any rust or corrosion at mounting points.
• Step 4 – Observe flame: After reassembly, call for heat and observe the flame. It should be blue and stable. If flames are weak or lifting, have a gas technician check inlet and manifold pressure.
• Step 5 – Test flame signal (technician): A professional can measure microamp flame current between the flame sensor and control board. If the signal is low despite good flame, the Tempstar control board may need replacement.