Furnace blower runs continuously; burners do not fire; LED status light flashes eight times repeatedly.

Critical safety warning: An open rollout or secondary limit indicates overheating or flame rollout. Shut off the furnace and inspect carefully. Do not bypass safety switches.

Step-by-step checks:

• 1. Inspect for visible damage: With power off, remove the burner door. Look for melted wires, soot, or scorch marks around the burners and heat exchanger.
• 2. Check rollout switches: Locate the small manual-reset rollout switches near the burners. If a reset button is present, press it once to reset. If it immediately trips again on the next cycle, stop and call a technician.
• 3. Verify venting and heat exchanger area: Ensure the flue pipe is intact and not collapsed. Check for obstructions at the vent termination outside.
• 4. Confirm blower operation: Make sure the blower starts promptly after burner ignition (if the furnace will run at all). A delayed or failed blower can cause overheating.

When to call a professional: Repeated trips of secondary limits or rollout switches require professional diagnosis of the heat exchanger, venting, and combustion. Replacement of the affected Philco safety switches and possibly the heat exchanger may be necessary.