Lennox Heat Pump Error Code DS2:ON / DS1:ON

DS2:ON / DS1:ON indicates an internal component failure on the defrost control board. The board's self-diagnostic system has detected a fault originating inside the board itself, not from an external sensor or wiring issue. This means the board cannot reliably manage defrost operations and requires attention from a qualified technician.

The only DIY-appropriate step is cycling the 24-volt power to the board to see if the code clears. Beyond that, the repair involves replacing the defrost control board, which requires disconnecting electrical components and working inside the unit. This work is best performed by a licensed HVAC technician, both for safety reasons and to ensure the correct board is installed.

If the power cycle does not clear the code, the defrost control board will need to be replaced. Parts and labor costs can vary depending on your region, the specific board required, and the service provider, but repairs of this type typically range from $200 to $600 or more. Getting a quote from a licensed HVAC technician before proceeding is advisable.

Cycling the 24-volt power to the defrost control board is the first recommended step and may clear the code if the fault was caused by a temporary signal anomaly or power fluctuation. If the code returns after the power cycle, the board has a confirmed internal hardware failure and resetting will not resolve it. In that case, the board must be replaced.

With a failed defrost control board, the heat pump cannot reliably execute defrost cycles. In cold weather, this can allow ice to accumulate on the outdoor coil, which reduces efficiency and can cause compressor damage over time. Continued operation is not recommended until the fault is resolved.