What It Means
Indoor room temperature sensor T1 open or shorted.
Carrier Ductless Mini-Split
Carrier Ductless Mini-Split Error Code E4
Troubleshooting guide for the Carrier Ductless Mini-Split system fault E4.
Possible Causes
- Damaged T1 sensor wiring or loose connector.
- Out-of-calibration or failed T1 thermistor.
- Corroded sensor terminal connection.
Not sure which one it is — or if it's none of these? Try ACLogics today.
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.
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Full Diagnosis
Indoor Room Temperature Sensor T1 Open or Short. Indoor room temperature sensor T1 open circuit or short circuit.
All Recorded Causes
Check T1 sensor wiring and connector for damage or corrosion. Measure sensor resistance and compare to temperature/resistance chart. Replace T1 sensor if resistance is outside specifications.
Verify Before Replacing Parts
- Confirm the exact Carrier model family and ductless systems context before acting on a generic code description.
- Confirm filter condition, blower operation, and coil cleanliness before replacing any controls — start by ruling out whether check T1 sensor wiring and connector for damage or corrosion.
- Measure airflow-related readings that match the symptom, such as temperature split or static pressure, and check whether measure sensor resistance and compare to temperature/resistance chart.
- After the correction, run the system long enough to confirm the ductless systems fault does not return under normal load.
Still unsure about this fault?
ACLogics walks you through Carrier Ductless Mini-Split diagnostics step-by-step — so you confirm the cause before swapping parts.
