Lennox Furnace Error Code LED1 SLOW FLASH / LED2 SLOW FLASH

This code means your Lennox furnace is powered on and operating normally. Both diagnostic LEDs flashing slowly is the control board's way of confirming it has initialized correctly and is ready to respond to thermostat commands. This same pattern appears during heating, cooling, and continuous fan operation. No service action is required.

Yes, this LED pattern specifically indicates normal, safe operation. It confirms the control board has power and has passed its internal self-check. There are no safety concerns associated with the slow flash status code, and the furnace is designed to display this pattern continuously during normal use.

There is no repair cost associated with this code because it indicates normal operation, not a fault. If you are experiencing a comfort problem alongside this code and a technician diagnoses a separate underlying issue, repair costs will vary based on the specific component involved. Typical furnace service call fees range from $75 to $150, with parts and labor costs depending entirely on what component, if any, requires attention.

No repair is needed when this code is displayed. LED1 SLOW FLASH / LED2 SLOW FLASH is a status indicator, not a fault code. If your system is heating, cooling, or moving air as expected, the furnace is functioning correctly. If comfort issues persist despite this normal status code, the problem likely lies in the thermostat, ductwork, or a specific downstream component rather than the control board itself.

Resetting the furnace will not change this code because it is not a fault condition that needs to be cleared. After a reset or power cycle, the control board will simply return to displaying the slow flash pattern once it powers back on and completes its startup sequence. A reset is unnecessary and will not affect system performance.