LED flashes code 13; furnace locks out and will not restart for about 3 hours unless power is cycled.

Warning: Limit and rollout trips can indicate unsafe overheating or flame rollout. Turn off power and gas to the furnace before inspection. If you see signs of scorching, melted wiring, or warped metal, contact a professional immediately.

• Step 1 – Reset power: Turn off power to the furnace for 30 seconds to clear the lockout. Restore power and observe operation.
• Step 2 – Inspect limit and rollout switches: Locate the primary limit switch on the heat exchanger panel and any rollout switches near the burners. Check for manual reset buttons on rollout switches and press gently if present. If a rollout switch has tripped more than once, do not keep resetting—find and correct the cause.
• Step 3 – Check airflow: Replace or clean the furnace filter. Ensure all supply registers and return grilles are open and unobstructed. Inspect the Tempstar A-coil (evaporator coil) for dirt buildup; if heavily clogged, have it professionally cleaned.
• Step 4 – Inspect venting and combustion air: For high-efficiency Tempstar furnaces, check PVC intake and exhaust pipes for blockages (ice, leaves, nests). For standard models, inspect the metal flue for obstructions.
• Step 5 – Test switches: With power off, disconnect wires from the limit and rollout switches and test continuity with a multimeter. Replace any switch that remains open at room temperature.
• Step 6 – Call a technician if rollout is suspected: If rollout switches trip repeatedly or you see flame escaping the burner area, shut the system down and have a certified technician inspect the heat exchanger and burner assembly.