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

DS2:OFF / DS1:OFF indicates that the defrost control board is not receiving 24-volt AC power at its R and C terminals, or that the board itself has failed. Both status LEDs on the board are unlit, meaning the board is completely inactive. This condition prevents the unit from performing defrost cycles and requires diagnosis of the low-voltage power supply circuit.

A simple power reset will not clear this condition if the underlying cause is still present. Because the board is receiving no power, it cannot store or display a fault that a reset would resolve. The root cause, whether a failed transformer, blown fuse, or board failure, must be repaired before the board will power on and operate normally.

Repair costs depend on the failed component. A replacement control transformer typically costs between $30 and $100 in parts, while a defrost control board can range from $80 to $250 or more depending on the model. Adding a technician's diagnostic and labor fees, total repair costs commonly fall between $150 and $450, though this varies by region and the specific parts required.

Some causes, such as a tripped breaker or a loose wire connection at the board terminals, can be addressed by a knowledgeable homeowner. However, testing transformer output voltage, tracing low-voltage wiring faults, and replacing the defrost board require basic electrical knowledge and a multimeter. If you are not comfortable working around electrical components, a licensed HVAC technician should handle the diagnosis.

Operating the heat pump without a functioning defrost board means the unit cannot initiate defrost cycles. During cold weather, this can cause excessive ice buildup on the outdoor coil, which reduces efficiency and can cause compressor damage over time. It is advisable to have the system diagnosed and repaired promptly to avoid secondary damage.