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Lennox · Heat pump

E413 High pressure switch strikes lockout

High severity

What the control is telling you

High pressure switch opened five times in one cooling demand; the outdoor unit is shut down. S30/S40 thermostat alert code 413 (shown as E413 on the unit control display).

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

Likely causes

  • Overcharge
  • Outdoor fan failure
  • Dirty coil or blocked airflow

Test and repair steps

  1. Check charge using superheat and subcooling.
  2. Check outdoor fan operation.
  3. Remove dirt or debris blocking airflow.
  4. Reset by putting the outdoor control in test mode or cycling low-voltage power.

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.30. 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.