Lennox Unit controller

Lennox Unit controller Error Code 228

Unit controller

What It Means

  • SST SENSOR FAILURE COMPRESSOR 3

Causes & actions from Lennox

How it shows
  • M4 alarm code: 228

Saturated Suction Temperature sensor on the evaporator coil is not giving expected values for the indicated compressor circuit. Alarming Values: 1 – Open Circuit: Less than or equal to -66°F (res >= 930kohms) 2 – Short Circuit: Greater than or equal to 500°F (res <= 24ohms) 3 – Out of Range: Less than -40°F or greater than 150°F 4 – Dislodged (operational check) If alarm indicates “open”, “short” or “out of range” check sensor and wiring. Alarm clears when in-range condition is detected. If alarm indicates “dislodged”, check that the sensor is installed properly and is seated properly to the fitting and is not loose or improperly installed. Alarm clears on a controller reset.

Applicable models & manual sources
Disclaimer: This information is for general reference. Code wording and instructions vary by model. Always follow the service manual for your exact unit.

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