Blower runs continuously; no heat; LED flashes eight times repeatedly.

Safety first: Turn off power before accessing internal components.

• Replace filter and open registers: Install a new clean filter and ensure most supply and return registers are open.
• Inspect blower wheel: With power off, remove the blower compartment door and inspect the blower wheel for dust buildup. Heavy buildup reduces airflow and can cause overheating. Cleaning the wheel often requires blower removal.
• Check limit switch continuity: With power off, test the high limit switch with a multimeter. If it shows closed when the furnace is cool and never opens during operation, it may be stuck and require replacement.
• Verify blower speed tap (advanced): On some Fraser‑Johnston furnaces, blower speed for heat is selected via wires on the control board. A technician can adjust to a higher speed to improve airflow.
• Reset control: After correcting airflow, cycle power to clear the fault. If the 8‑flash code returns, have a professional evaluate duct sizing and furnace setup.