Lennox Heat Pump Error Code DS2 SLOW Flash / DS1 OFF

This code indicates a High Pressure Fault, meaning the unit detected refrigerant pressure exceeding a safe limit on the high side of the system. Each occurrence adds one strike to the high pressure fault counter tracked by the control board. Common triggers include blocked coils, fan problems, and incorrect refrigerant charge. If the fault accumulates enough strikes, the unit may enter a lockout state.

The high pressure safety switch is designed to protect the compressor from damaging pressure levels, so the fault should not be ignored. Continued operation without identifying and correcting the root cause can stress the compressor and refrigerant circuit components. It is best to address the fault promptly, and if the unit is tripping this code repeatedly, shut it down until the cause is diagnosed.

Repair costs vary widely depending on the root cause. Cleaning coils or replacing an air filter may cost very little, while fan motor replacement typically runs in the range of $200 to $600 including labor. Refrigerant-related repairs such as recovering and recharging the system can range from $150 to $500 or more depending on refrigerant type and the amount needed. A service call for diagnosis alone generally falls in the $75 to $150 range.

Some causes are accessible to a knowledgeable DIYer, such as clearing debris from outdoor coils, replacing a dirty air filter, or confirming fan operation. However, diagnosing refrigerant charge issues, measuring system pressures against charging charts, and recovering or adding refrigerant require EPA Section 608 certification and gauges. If basic airflow checks do not resolve the fault, a licensed HVAC technician should evaluate the refrigerant circuit.

A reset may clear the current display and allow the unit to restart, but the fault counter on the control board retains the strike count. If the underlying cause of the high pressure condition is not corrected, the fault will recur and additional strikes will accumulate. Repeated resets without repairs can lead to a full lockout requiring a technician to manually clear the board.