Lennox Furnace Error Code LED#1 Simultaneous Slow Flash / LED#2 Simultaneous Slow Flash

This pattern means the furnace is powered on and operating normally. Both LEDs flashing slowly at the same time is a status confirmation from the control board indicating no faults are present. The same pattern also appears during cooling mode and continuous fan operation. No service or repair is needed when this pattern is displayed.

Yes, it is completely safe. The simultaneous slow flash on both LEDs is a positive status indicator confirming normal operation, not a warning or fault signal. Your furnace is operating within its designed parameters when this pattern is displayed.

No repair cost applies to this LED pattern because it indicates normal operation rather than a fault. If you called a technician specifically for this pattern and they confirm normal operation, you may incur a standard diagnostic or service call fee, which typically ranges from $75 to $150 depending on your region and provider.

No, this LED pattern does not indicate a problem. It is a normal operational status signal used by the Lennox control board to confirm the system is powered and functioning correctly. If you are experiencing comfort problems despite seeing this pattern, the issue is likely unrelated to the control board and may involve thermostat settings, airflow, or the heating or cooling equipment itself.

Resetting the furnace is not necessary and will not change this pattern in any meaningful way, because it is not a fault code. After a reset, the control board will power back up and display this same simultaneous slow flash pattern again as confirmation of normal operation. Resetting should only be considered if the LEDs are showing an actual fault pattern.