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

This code indicates a low pressure lockout. The heat pump's control board detected five separate low pressure faults during a single thermostat demand cycle (Y1), meaning the low pressure switch opened five times before the call for heating or cooling was satisfied. The system locks out the compressor at this point to prevent damage from running with insufficient refrigerant pressure.

The lockout is a protective function, so the compressor will not run while the fault is active. Attempting to repeatedly reset and restart the system without correcting the cause can accelerate compressor wear if the unit runs even briefly under low-pressure conditions. It is best to leave the system off until a technician can diagnose and repair the fault.

Diagnosis starts with a visual inspection of both the indoor and outdoor coils and fans for blockages, ice buildup, or collapsed filters. The technician then connects gauge manifolds to measure operating suction and discharge pressures, and cross-references those readings with approach temperature and subcooling values to assess system charge. Wiring and operation of the low pressure switch are also verified. If pressures are low, a leak search is performed before any refrigerant is added to the system.

You can reset the lockout by cycling power to the unit, but this will not resolve the underlying cause. If the root problem, such as low refrigerant, blocked coils, or a faulty pressure switch, is not corrected, the system will accumulate five more low pressure faults and lock out again. A full diagnosis of operating pressures, airflow, and system charge is necessary before the unit will run reliably.

Repair costs vary significantly depending on the root cause. Clearing a blocked coil or replacing a low pressure switch typically costs in the range of $100 to $300 for labor and parts. If a refrigerant leak is involved, leak detection, repair, and recharge can range from $300 to $800 or more depending on the leak location and refrigerant type. A failed metering device replacement may fall in the $250 to $600 range including labor.