Lennox Heat Pump Error Code Alternating SLOW Flash (Green/Red)

The alternating slow green and red LED flash indicates the unit is in a 5-minute anti-short cycle delay. This delay activates after initial power-up, after a safety trip, or at the end of a thermostat demand cycle. It is a protective timing function that prevents the compressor from restarting before refrigerant pressures equalize. The system will resume normal operation automatically once the 5-minute period ends.

The unit is not running during this condition as the compressor is held offline by the delay timer. The system is in a controlled standby state and there is no safety risk to the equipment or occupants. The heat pump will restart automatically once the delay period expires.

If the alternating slow flash is due to normal power-up or end of thermostat demand, there is no repair cost involved. If the delay is being triggered by an underlying fault such as a refrigerant charge issue or a faulty pressure switch, diagnostic and repair costs will vary depending on the specific problem found. A refrigerant recharge service typically ranges from $150 to $400, while pressure switch replacement can range from $75 to $250 including labor.

In most cases, no action is required. The delay clears automatically after 5 minutes and the unit resumes normal operation. If you are a technician performing diagnostics and need to bypass the delay, you can jumper the TEST pins on the control board to override it. If the delay is being triggered repeatedly by safety trips, the underlying cause should be investigated.

Resetting power will not bypass the delay and will actually restart the 5-minute timer from the beginning, since power-up is one of the three conditions that triggers the anti-short cycle delay. The correct approach is to simply wait out the 5-minute period. Technicians can use the TEST pin jumper to override the delay without cycling power.