York Furnace Error Code LED on constantly

A constantly illuminated LED on a York furnace means the control board detected an internal fault during its own self-check procedure. When this fault is found, the control immediately stops all furnace operations, including heating and blower functions. The furnace will remain shut down until the fault is resolved through a reset or board replacement.

Start by checking the supply voltage at the furnace disconnect to confirm it is within the correct operating range and look for evidence of power surges. Then break line voltage to the unit for 30 seconds and restore power to allow the board to re-run its self-check. If the constant LED condition returns immediately, the control board will need to be replaced by a qualified technician.

If only a reset is needed, there is no parts cost, though a service call to diagnose the voltage conditions may run in the range of $75 to $150 depending on your area. If the control board requires replacement, parts and labor combined typically range from $300 to $650, depending on the specific board and local labor rates. Addressing underlying power quality issues such as installing a surge protector may add additional cost but can prevent repeat failures.

A reset can clear the fault if the root cause was a temporary voltage spike or transient power disturbance. To reset the control, disconnect line voltage to the furnace for a full 30 seconds, then restore power. If the LED comes back on constantly after the reset, the control board has a permanent internal failure and must be replaced.

No, the furnace has already shut itself down completely as a result of this fault. The control board intentionally halts all operations when it detects an internal fault, so the furnace will not ignite or run in this state. You should not attempt to bypass or override the board, and the fault should be diagnosed and corrected before returning the furnace to service.