What It Means
Outside air temperature (OAT) sensor out of valid range.
Carrier Packaged Unit
Carrier Packaged Unit Error Code 73
Troubleshooting guide for the Carrier Packaged Unit system fault 73.
Possible Causes
- Damaged OAT thermistor wiring or loose connector.
- Out-of-calibration or open thermistor.
- Incorrect sensor routing or thermal exposure.
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
Outside Air Temperature Failure. Outside-air temperature is outside the valid range; usually caused by faulty thermistor, wiring error, or loose connection.
All Recorded Causes
Check OAT sensor wiring, connector, and routing. Measure sensor resistance and compare to chart. Inspect for wiring errors or open circuits. Replace OAT thermistor if resistance is outside specifications.
Verify Before Replacing Parts
- Confirm the exact Carrier model family and outdoor packaged units context before acting on a generic code description.
- Verify the sensor or thermistor reading against the expected range for the current operating condition, keeping in mind that check OAT sensor wiring, connector, and routing.
- Check the sensor harness and board connection before condemning the sensor itself; on Carrier units this is also where you'd confirm measure sensor resistance and compare to chart.
- After the correction, run the system long enough to confirm the outdoor packaged units fault does not return under normal load.
Still unsure about this fault?
ACLogics walks you through Carrier Packaged Unit diagnostics step-by-step — so you confirm the cause before swapping parts.
