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

This code indicates a discharge line temperature fault. The heat pump's control board detected that the discharge line temperature exceeded 285°F (140°C) during compressor operation, which triggered a protective compressor lockout. The fault can be caused by a shorted temperature sensor or by actual high discharge temperatures resulting from airflow restrictions, refrigerant charge issues, or a faulty metering device. The compressor will not restart until the discharge temperature drops below 225°F (107°C).

The control board has already protected the system by locking out the compressor when this fault triggers, so the unit will not run the compressor in a damaging state during the lockout period. However, you should not attempt to repeatedly reset the unit and force it to restart without identifying the root cause. Continued operation under high discharge temperature conditions can degrade compressor lubrication and lead to complete compressor failure.

Repair costs vary depending on the root cause. A simple service call to clean coils, check airflow, and verify refrigerant charge might run in the range of $100 to $300. If the discharge line temperature sensor needs replacement, parts and labor could range from $150 to $400. A refrigerant recharge typically adds $150 to $500 depending on refrigerant type and the amount needed. Metering device replacement is more involved and could range from $300 to $700 or more. A compressor replacement, if damage has already occurred, is significantly more expensive.

Some portions of the diagnosis are DIY-friendly, such as checking and replacing air filters, clearing debris from the outdoor unit, and confirming airflow is not blocked at supply or return vents. However, diagnosing refrigerant charge, testing the metering device, and replacing the discharge line sensor typically require specialized tools and refrigerant handling certification. It is recommended to contact a licensed HVAC technician for anything beyond basic airflow checks.

A reset may temporarily clear the fault code and allow the compressor to attempt a restart, but only after the discharge temperature drops below 225°F (107°C). If the underlying cause, such as restricted airflow, low refrigerant charge, or a faulty sensor, is not corrected, the fault will return once the system runs and temperatures rise again. Resetting without diagnosis is not a fix and can lead to repeated fault cycles.