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Lennox · Furnace

E154 Refrigerant leak sensor #1 communication lost / wrong DIP setting

High severity Lennox ML180UHE

What the control is telling you

The control cannot talk to refrigerant detection sensor #1, or the Low GWP DIP switches do not match the sensors fitted. The blower latches on for at least 5 minutes after communication returns.

Applies to: ML180UHEK (R-454B era) single-stage 80% furnaces with integrated control 107792-XX (ML180UH045/070/090/110/135, incl. low-NOx X models)

Likely causes

  • Damaged or unplugged sensor #1 wiring harness or connector
  • Sensor #1 damaged or plug obstructed
  • LGWP DIP switches set wrong (e.g. Enable with no sensor fitted)
  • Furnace-only / R410A job with sensors still enabled

Test and repair steps

  1. Check the LGWP DIP switches (Table 17) one sensor = LGWP1 Enable / LGWP2 Disable; two sensors = both Enable; no sensor (R410A or heat only) = both Disable. LGWP1 Disable with LGWP2 Enable is invalid.
  2. On a furnace-only or non-low-GWP job set both switches to Disable, otherwise the blower runs continuously.
  3. Check the sensor #1 cable is seated in the SENSOR 1 (LGWP1) plug with the Molex clip locked and no dust or moisture.
  4. Inspect the harness for damage along its route and at the evaporator coil.
  5. Press the LGWP test button on the control to retest once repaired.

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Source: Lennox ML180UHEK Unit Information 100161/100166, Table 6 Integrated Diagnostic Codes, p.14; Table 17 LGWP DIP switch settings, p.33. 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.