Lennox Heat Pump Error Code DS2 ON / DS1 ON

The DS2 ON / DS1 ON code indicates an internal component failure on the defrost control board. The defrost control board manages how and when the heat pump clears ice from the outdoor coil, and this code means the board itself has malfunctioned. The fault is board-level, meaning it cannot be resolved by addressing external sensors or wiring alone. A power cycle is the first diagnostic step, followed by board replacement if the code does not clear.

Operating the heat pump with a failed defrost control board is not recommended. Without a functioning defrost board, the outdoor coil can accumulate heavy ice buildup, which reduces efficiency and can cause compressor damage over time. It is best to address this fault promptly to avoid secondary damage to other system components.

Yes, if the code persists after cycling 24-volt power to the control, replacing the defrost control board is the correct and final repair. The code specifically points to an internal board failure, and there is no field-level repair for the board's internal components. Once a functioning replacement board is installed, the system should resume normal defrost operation.

You can attempt a reset by cycling the 24-volt control power to the unit, which means shutting off power to the system, waiting briefly, and restoring it. If the code clears and does not return, the fault was likely a transient issue. If the code comes back after the reset, the control board has a persistent internal failure and will need to be replaced by a qualified technician.

Repair costs depend on whether the issue resolves with a simple power cycle or requires a full control board replacement. If board replacement is needed, parts and labor costs typically range from $200 to $600 or more depending on the specific board, your region, and the technician's rates. Getting a diagnostic service call first is the best way to confirm the repair needed before committing to parts costs.