Status LED flashes code 34 (three short, four long). Furnace attempts ignition but flame is weak or goes out quickly.

Safety first: Turn off power and gas before removing the burner access panel. Flame sensing is a safety function; do not bypass it.

• Clean flame sensor: Locate the flame sensor (small metal rod in front of a burner with a single wire). Remove the mounting screw and gently clean the rod with fine steel wool or a Scotch-Brite pad. Do not sand the porcelain. Reinstall and reconnect the wire.
• Check sensor position: Ensure the sensor tip is directly in the burner flame when burners are lit.
• Inspect ground connections: Verify the burner rack and control board ground wires are tight and free of rust. Clean contact points if corroded.
• Observe flame quality: With the panel back on and power restored, call for heat. Flames should be blue and stable. Yellow, lifting, or noisy flames may indicate gas pressure or burner issues that require a technician.
• Replace flame sensor if needed: If cleaning does not resolve the issue and the sensor shows signs of cracking or heavy corrosion, replace it with a Payne-compatible flame sensor.