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Lennox · Air conditioner

E183 Outdoor liquid pressure sensor fault

Medium severity

What the control is telling you

Liquid pressure sensor reading under 0.25 V or above 4.75 V for 24 h (+/- 3 h) or more; normal operation continues. S30/S40 thermostat alert code 183 (shown as E183 on the unit control display).

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

Likely causes

  • Failed sensor or wiring

Test and repair steps

  1. Check the sensor wiring and connector.
  2. Replace the sensor if out of range.
  3. See the unit literature on low pressure switch emulation.
  4. Resets after 3 consecutive in-range readings.

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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.18. 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.