Lennox Heat Pump Error Code DS2 OFF / DS1 SLOW Flash

This code indicates a low pressure fault where the low-pressure switch has tripped and the control board has recorded one strike. The system shut down to protect the compressor from running under low-pressure conditions. The most likely causes are restricted airflow, a low refrigerant charge, or a loose pressure switch connection.

The system has already shut down to protect the compressor, so it is not running normally. Continuing to attempt operation without addressing the root cause can cause the fault counter to accumulate additional strikes and potentially lead to compressor damage. It is best to diagnose and resolve the underlying issue before resuming normal operation.

A power reset may clear the active fault display, but if the underlying condition causing low pressure is still present, the switch will trip again and additional strikes will be logged. Resetting without diagnosing and correcting the root cause is not a reliable fix and risks escalating the fault to a higher-strike lockout. The fault should be fully investigated before relying on a reset.

Some steps are DIY-friendly, such as clearing debris from coils, checking for obvious blockages around the outdoor unit, and inspecting fan operation. However, diagnosing refrigerant charge requires gauges and knowledge of the unit's charging charts, and adding refrigerant requires EPA certification. If airflow checks do not resolve the fault, a licensed HVAC technician should handle the refrigerant-side diagnostics.

Repair costs vary widely depending on the cause. Clearing a blocked coil or securing a loose connection is a low-cost service call, typically in the range of $75 to $200. If the system needs refrigerant added due to a leak, costs can range from $200 to $600 or more depending on refrigerant type, the amount needed, and any leak repair required. A failed fan motor replacement can range from $150 to $500 depending on the part and labor involved.