Lennox Heat Pump Error Code Green SLOW Flash / Red OFF

This code indicates a high pressure fault, meaning the refrigerant system's high pressure switch tripped and shut down the compressor to prevent damage. The switch opens when refrigerant pressure exceeds a safe threshold on the high side of the circuit. The most common triggers are restricted airflow at the coils or a fan motor that is not operating correctly. The system will not resume normal operation until the cause is addressed and pressure returns to a safe level.

No, you should not attempt to force the system to run while this fault is active. The high pressure switch trips to protect the compressor and refrigerant lines from pressures that can cause mechanical failure or rupture. Repeatedly resetting the unit without correcting the underlying cause risks permanent compressor damage, which is significantly more expensive to repair than the original fault condition.

Repair costs vary widely depending on the cause. Cleaning a coil or clearing a blockage may cost relatively little if done as part of a service call, typically in the range of $75 to $200. Replacing a failed fan motor can range from $250 to $600 or more depending on the motor and labor involved. If the compressor was damaged by repeated high pressure trips, replacement costs can reach $1,200 to $2,500 or higher. Early diagnosis keeps repair costs at the lower end of the range.

Some causes of this fault are accessible to a knowledgeable DIYer, such as removing debris from around the outdoor unit, cleaning a dirty coil, or confirming that both the indoor and outdoor fans are spinning freely. However, diagnosing issues like refrigerant overcharge, a failed high pressure switch, or a motor drawing incorrect current requires gauges and electrical test equipment. If basic airflow checks do not resolve the fault, a qualified HVAC technician should complete the diagnosis.

The system may reset automatically once refrigerant pressure drops back to a normal level, and in some cases cycling the unit off at the thermostat or breaker will allow it to restart. However, if the root cause has not been corrected, the high pressure switch will trip again shortly after the compressor restarts. Repeated resets without diagnosis can accelerate compressor wear, so the cause should be identified and fixed before relying on a reset.