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Lennox · Air conditioner

E435 Inverter EEPROM checksum fault (inverter code 60)

High severity

What the control is telling you

Inverter internal error; the outdoor control cycles inverter power (contactor open two minutes) three times, then locks out. Inverter LED flash code 60 (red 6 flashes, green off). S30/S40 thermostat alert code 435 (shown as E435 on the unit control display).

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

Likely causes

  • Inverter internal fault

Test and repair steps

  1. Refer to the unit service manual.
  2. Clear by disconnecting power to the outdoor unit and restarting; replace inverter if it repeats.
  3. Check inverter LEDs flash code 60 = red 6 flashes, green off. Normal inverter LEDs with no fault: red ON, green OFF.

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.40. 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.