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T121

T121 - Circuit B Low Saturated Suction Temperature Alert

Carrier · Air Conditioning

What does T121 mean?

An alert indicating low suction temperature in Circuit B. The circuit will stop as a precaution.

Common Causes

  • Low refrigerant charge
  • Low airflow
  • Dirty coil
  • Broken fan belt
  • TXV problem

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Replace the air filter if it is dirty.

  2. 2

    Ensure the evaporator coil is clean.

  3. 3

    Check that the indoor fan is running properly.

  4. 4

    A technician should inspect the refrigerant charge and TXV.

Browse all codes in this manual (60)
Verified technical data. Last updated: April 2026

Related Faults

A051A051 - Compressor 1 Stuck On FailureA052A052 - Compressor 2 Stuck On FailureA055A055 - Compressor 1 Stuck On Failure (Circuit B)
Source: Carrier Air Conditioning
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