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Lennox · Heat pump

Red LED on / Green LED off Inverter board normal (no fault)

Normal status

What the display is showing

On inverter outdoor units the inverter board shows a steady red LED and an unlit green LED when everything is fine. Any fault is shown by the red and green LEDs flashing a set number of times instead.

Applies to: Lennox inverter outdoor units (air conditioner and heat pump) in S30/S40 communicating systems

Settings for these units

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 inverter alert code notes (e.g. alert 423, inverter flash code 40), p.32. Summarized in our own words; check the original manual for your model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.