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Lennox · Air handler

E354 Electric heat stage 4 fault

Medium severity

What the control is telling you

Air handler fourth-stage electric heat fault: its pilot relay coil was not energized or the contacts stayed open. S30/S40 alert code 354; unit control shows E354.

Applies to: Lennox communicating air handlers and EIM-equipped indoor units in S30/S40 smart thermostat systems

Likely causes

  • Failed heat relay/sequencer
  • Open heating element or limit
  • Wiring fault

Test and repair steps

  1. Check 24 VAC to the stage relay coil and whether the contacts close.
  2. Check element continuity and limits for that stage.
  3. The air handler runs on first-stage electric heat until fixed.
  4. Clears after the fault recovers.

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.27. 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.