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Lennox · Furnace

E344 IFC relay Y1 stuck

High severity

What the control is telling you

Possible Y1 relay failure on the integrated furnace control (IFC). S30/S40 thermostat alert code 344 (shown as E344 on the unit control display).

Applies to: Lennox communicating gas furnaces (e.g. SL280UHV/SL280UHNV, EL296UHV) in S30/S40 smart thermostat systems

Likely causes

  • Y1 relay on the IFC stuck

Test and repair steps

  1. Check whether Y1 output stays energized with no cooling call.
  2. If the issue continues, replace the integrated furnace control.
  3. Clears five minutes after Y1 input is sensed off.

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.25. 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.