HVACopedia

Lennox · Air conditioner

E442 Compressor top cap switch strikes lockout

High severity

What the control is telling you

Compressor thermal protection opened five times within one hour; outdoor unit locked out. S30/S40 thermostat alert code 442 (shown as E442 on the unit control display).

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

Likely causes

  • Compressor overheating (charge, airflow, TXV)

Test and repair steps

  1. Find why the compressor overheats (charge, outdoor fan, TXV, indoor blower).
  2. Clear by disconnecting power to the outdoor unit 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.43. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

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.