AL10
Carrier Transicold
Warning
Alarm 10 – Supply Air Temperature Sensor (SATS) Out of Range
Carrier Transicold alarm AL10 (Alarm Code 10) means the Advance microprocessor has detected the Supply Air Temperature Sensor (SATS/STS) reading is out of range, open, or shorted. The SATS lives in the discharge airstream after the evaporator on Vector, X4, X2 and Supra reefer units and is the primary control sensor when 'Supply' is selected. When AL10 latches, the controller falls back to the Return Air Sensor and box temperature control becomes unstable — a frequent cause of load-quality claims.
Possible causes
- Failed SATS thermistor — resistance out of spec (should be ~32.6 kΩ @ 0°C / 32°F)
- Broken, chafed, or pinched sensor wiring between the evaporator and the controller
- Corroded or water-filled sensor connector at the evaporator housing
- SATS pulled out of its clip and hanging in still air (giving false ambient reading)
- Ice buildup around the sensor blocking accurate airflow reading
- Damaged Advance controller input channel
Recommended actions
- Compare SATS vs RATS in the controller data menu — a difference greater than 5°F/3°C with fans running points at SATS.
- Disconnect the SATS at the controller and measure resistance vs the Carrier temperature-vs-resistance table (32.6 kΩ @ 0°C).
- Inspect the sensor harness end-to-end for rubs against the evaporator frame and check for green corrosion inside the connector.
- Confirm the sensor is fully seated in its mounting clip in the discharge airstream, not resting on the coil.
- Force a defrost and re-check — if AL10 clears after defrost, the coil was iced over the sensor.
- If harness and sensor test good, swap the SATS input at the controller with a known-good channel to isolate a bad controller input.
- After replacing the sensor, clear alarms and run a full Pretrip (PTI) to confirm AL10 does not return.
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