System Diagnosis
Outdoor Coil Sensor Fault. Coil sensor not reading or out of range.
Carrier | Air Conditioners
Error Code 55
Troubleshooting guide for the Carrier Air Conditioners system fault 55.
Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.
Potential Causes & Solutions
- Ohm out the outdoor coil temperature sensor and compare to temperature/resistance chart.
- Check sensor wiring and connector.
- Verify sensor is properly seated on the coil.
- Replace sensor if out of spec.
Verify Before Replacing Parts
- Confirm the exact Carrier model family and air conditioners context before acting on a generic code description.
- Confirm filter condition, blower operation, and coil cleanliness before replacing any controls.
- Measure airflow-related readings that match the symptom, such as temperature split or static pressure.
- After the correction, run the system long enough to confirm the code does not return under normal load.
Field Signals to Confirm
What usually confirms it
Weak airflow, abnormal temperature split, or repeated protective trips tied to blower performance.
What can fool you
Charge and control faults often look similar until airflow and coil condition are verified first.
When to Escalate the Call
- The code returns after airflow and cleanliness checks are corrected.
- You find evidence of duct or static issues that require a larger system review.
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