General Assist Customer Guidance

Defrost Symbol – What It Means

Understanding automatic defrost operation while your air conditioner is heating
If the defrost indicator appears on your controller, the system is temporarily removing frost from the outdoor heat exchanger. This is a normal and automatic part of heating operation and does not usually indicate a fault.

1. Why defrost mode happens

During heating operation, the outdoor unit absorbs heat from the outside air. In cold or humid weather, moisture can freeze on the outdoor heat exchanger. If this frost is allowed to build up, it can reduce airflow and heating performance.

The air conditioner therefore enters an automatic defrost cycle to melt and remove the frost before returning to normal heating.

What may happenWhat it means
The outdoor fan stopsThis allows the system to warm the outdoor heat exchanger and clear the frost.
The indoor fan slows or stopsThis helps prevent cool air from being circulated into the room during the cycle.
Heating pauses temporarilyNormal heating resumes automatically after defrost is complete.
Water or steam appears outsideMelting frost may drain from the outdoor unit, and vapour may be visible in cold weather. This can be normal.

2. How long does defrost take?

A defrost cycle will commonly last several minutes. The exact duration and frequency depend on outdoor temperature, humidity, system load and the amount of frost on the outdoor heat exchanger.

Typical operation: Many systems complete defrost within approximately 4–15 minutes, although actual operation can vary with the model and weather conditions.

In cold or humid conditions, defrost may occur more often. This is part of the system’s normal control process.

3. What you may see on the controller

The controller may display a defrost indicator while the system is temporarily clearing frost from the outdoor unit.

Example controller display. The appearance and location of the indicator may vary by controller model.
No action is normally required. Leave the system switched on. The indicator should disappear and heating should resume automatically once defrost is complete.

4. What you may notice in the room

  • Warm airflow may stop for a short period.
  • The room may feel slightly cooler while heating is paused.
  • The indoor fan may remain stopped briefly after defrost while the heat exchanger warms up.
  • Normal heating should then restart without any manual input.

5. When to contact your installer or service agent

Arrange further assessment when:

  • the defrost indicator remains displayed for an unusually long period;
  • the system does not return to heating operation;
  • heating output remains poor after the cycle has finished;
  • an error code is displayed; or
  • the outdoor unit is heavily iced and does not appear to clear itself.
Do not attempt to remove ice using sharp tools, boiling water or an open flame. This may damage the unit or create an electrical or personal-safety risk.

6. Summary

  • Defrost is a normal part of heating operation.
  • The outdoor unit temporarily melts frost from its heat exchanger.
  • Heating and fan operation may pause for several minutes.
  • The system should return to heating automatically.
  • Further assessment is recommended if defrost does not finish or heating does not resume.

Support

Assist Technical Support
Australia: 1300 364 484
New Zealand: +64 4 568 8761
Controller symbols and operating behaviour can vary by product and controller model. Refer to the applicable operating manual for model-specific information.