LED flashes slowly indicating soft or hard lockout, furnace will not attempt ignition until reset.

Safety First: Do not repeatedly reset a furnace that fails to ignite; unburned gas can accumulate. Turn off gas and power if you smell gas.

Lockout occurs after multiple failed attempts to start.

• Reset procedure: Turn off power to the furnace for at least 30 seconds, then restore power. Some thermostats also require cycling from HEAT to OFF and back.
• Review prior fault code: Many Thermo Pride boards will show the last fault code before lockout. Note the flash pattern before resetting and address that underlying issue (e.g., flame sensor, pressure switch, limit).
• Inspect basic items: Check filter, gas supply, and venting before attempting another start.

When to call a professional: If the furnace repeatedly goes into lockout, a technician must diagnose the root cause rather than continuing to reset.