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Troubleshooting code

Back to all 5TWX6018A1 error codes

Trane 5TWX6018A1 1 Flash troubleshooting

Ambient temperature sensor out of range. Use this page to document the issue and prepare for service. GreenFlow should handle diagnosis for electrical, refrigerant, lockout, or recurring conditions.

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What the code means

1 Flash: Ambient temperature sensor out of range

The Trane defrost control indicates the ambient temperature sensor is out of range, open, or shorted.

System area
Outdoor ambient sensor
Service level
Service recommended

Safe checks before calling

  • Confirm the thermostat is on, set correctly, and calling for heating or cooling.
  • Check the air filter and visible return-air path for obvious airflow restrictions.
  • Look around the outdoor unit for leaves, snow, ice, or other visible obstructions without opening the cabinet.
  • Take photos of the thermostat, outdoor unit, nameplate, and any visible flash pattern before scheduling service.

When to stop and call GreenFlow

Call GreenFlow if the code repeats, the system is locked out, heating or cooling is not restored, there is ice buildup, electrical odor, unusual noise, or any issue involving pressure switches, sensors, wiring, refrigerant, reversing-valve operation, or warranty coverage.

Share the visible code, model and serial number if available, photos, current symptoms, and whether the issue affects heating, cooling, or both.

1 Flash questions

What does 1 Flash mean on a Trane 5TWX6018A1?

The Trane defrost control indicates the ambient temperature sensor is out of range, open, or shorted.

What Trane message is associated with 1 Flash?

The Trane source used for this page associates 1 Flash with "Ambient temperature sensor out of range". Match the visible display text, LED pattern, or alert wording to the exact code whenever possible.

What system area does 1 Flash point to?

This code is grouped under outdoor ambient sensor in the source-backed Trane troubleshooting data.

Which Trane documentation supports this 1 Flash page?

Source-backed Trane ODR-SVX022B-EN LED fault-code table for 5TWX6 heat pumps.

Is 1 Flash an LED or flash-pattern code?

Yes. The Trane source row for this item is based on a displayed LED or flash pattern. Count the pattern exactly and compare it with the documented 1 Flash entry before interpreting the fault.

Is 1 Flash a sensor-related alert?

Yes. The documented row connects 1 Flash to outdoor ambient sensor. Sensor-related alerts should be interpreted by the exact code and operating mode rather than grouped with unrelated sensor faults.

Is 1 Flash related to defrost operation?

Yes. The Trane source row groups this item under defrost operation. The exact code matters because Trane separates different defrost fault patterns and causes.

Does 1 Flash involve a control, board, drive, or module?

The Trane source row points to outdoor ambient sensor. Record the exact code and visible alert text before any reset so the control history is not lost.

What information should be captured for 1 Flash before clearing alerts?

Capture the exact code, any displayed alert text, the model and serial number, thermostat or control status, operating mode, symptoms, and photos of the display or LED pattern before the alert history is cleared.

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