Lennox Furnace Error Code Off

The Off condition on a Lennox furnace means the control board is either receiving no power or has detected an internal fault that caused it to shut down completely. In this state, the furnace will not operate and no heating will occur. It is a baseline status indicating the board is not actively running any control logic.

Start by resetting the unit at the main power switch. Then check the circuit breaker at your electrical panel to confirm it has not tripped. If power is confirmed and the board is still unresponsive, inspect the small fuse located on the control board itself and replace it if blown. If none of these steps resolve the issue, a technician should test the transformer output voltage and evaluate the board for internal failure.

Repair costs vary widely depending on the cause. Resetting a tripped breaker or replacing a board fuse involves little to no cost. Transformer replacement typically falls in the range of $150 to $350 including labor. Control board replacement on a Lennox furnace generally ranges from $300 to $700 or more depending on the specific model and local labor rates.

Resetting the furnace by turning the main power switch off, waiting at least 30 seconds, and turning it back on can clear a latched board fault and restore normal operation. If the Off condition returns immediately after reset, a deeper electrical problem such as a blown fuse, failed transformer, or faulty board is likely present and will need further diagnosis.

A furnace showing the Off condition is not operating at all, so there is no immediate safety risk from active combustion or gas flow. However, you should not attempt to bypass the control board or force the unit to run without identifying the root cause. If you suspect wiring damage or a burnt component, do not restore power until those issues are inspected.