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Lennox · Air conditioner

E426 Excessive inverter alarms

High severity

What the control is telling you

10 inverter faults within 60 consecutive minutes; the control locks out. Inverter flash codes 12 to 14 and 53 do not count. S30/S40 thermostat alert code 426 (shown as E426 on the unit control display).

Applies to: Lennox communicating air conditioners incl. variable-capacity inverter units in S30/S40 smart thermostat systems

Likely causes

  • Repeated inverter faults

Test and repair steps

  1. Check the inverter history for the underlying fault code and fix it.
  2. Clear by disconnecting power to the outdoor control and restarting.

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.33. Summarized in our own words; check the original manual for your model.

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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.