Indoor Unit Fan Behaviour During Thermo-Off - RAC-0131
This article summarises Service Bulletin RAC-0131, issued 2 September 2026, covering changes to indoor-unit fan behaviour while the system is thermo-off.
Settings That Affect Fan Behaviour
| Setting | Function |
|---|---|
| FS49 | Indoor unit fan control for energy saving for cooling |
| FS43 | Cold air prevention |
| FS42 | Room temperature sensor switching |
| FS48 | Room temperature sensor switching (Aux.) |
| RC sensor setting | Enables or disables use of the wired remote controller room-temperature sensor |
| Fan control for energy saving | Wired remote controller energy-saving fan setting |
What Changed on the Applicable R32 Models?
The main change applies when the system is configured to use the wired remote controller as the room-temperature sensing point. In the relevant combinations of FS42, FS48 and the RC sensor setting, the indoor fan may now be OFF during thermo-off instead of continuing to run at low speed or intermittently.
FS42 = 01: Both
RC sensor = Used
FS48 = 01: Wired RC
The exact result also depends on operating mode, FS49 / FS43 and whether the system is single-split or multi-split.
Cooling and Dry - RAC and PAC
During thermo-off in Cooling or Dry, the indoor fan can operate in one of three ways depending on the model and settings:
- Follow the remote controller manual fan setting
- Intermittent fan operation
- Fan OFF on the applicable R32 models when the wired remote controller sensor configuration calls for it
FS49 options:
| FS49 | Setting |
|---|---|
| 00 | Disable |
| 01 | Enable |
| 02 | Controlled from remote controller (factory setting) |
Heating - Single Split RAC
For conventional R410A models and R32 models not listed in the affected-model section, the indoor fan generally operates at S-Lo during thermo-off.
On the applicable R32 models, the fan remains at S-Lo for the normal indoor-unit sensing arrangements, but can change to Fan OFF when the wired remote controller is selected as the active room-temperature sensor.
Heating - Single Split PAC
Ducted PAC models also use FS43 - Cold air prevention.
| FS43 | Thermo-Off Fan Behaviour |
|---|---|
| 00: Enable (factory setting) | Normally S-Lo. Applicable R32 models can change to Fan OFF when the wired RC sensor is selected. |
| 01: Disable | Fan follows the remote controller manual fan setting. If Auto is selected, fan speed is fixed at High. |
Note: The bulletin states FS43 is available only on duct units.
Heating - Multi Split
During heating thermo-off on multi-split applications, fan operation also depends on whether the outdoor compressor is operating for another connected indoor unit.
| System Condition | Typical Fan Behaviour |
|---|---|
| Compressor ON | Fan intermittent |
| Compressor OFF | Fan speed S-Lo |
On the applicable R32 models, when the wired remote controller sensor is selected as the active room sensor, the thermo-off fan can instead remain OFF.
Fan Intermittent - Cooling and Dry
When the control calls for intermittent fan operation during Cooling or Dry, the fan periodically runs at low airflow so that the indoor unit can sample room conditions.
| Indoor Unit | X | Y |
|---|---|---|
| High static pressure duct types 1 and 2 | 360 sec | 120 sec |
| Other models | 180 sec | 60 sec |
Airflow during the intermittent cycle varies by indoor-unit type. The bulletin identifies S-Lo / Lo / Quiet operation depending on the unit and stage of the cycle. In Dry mode, fan speed is additionally controlled by the Dry-operation logic for the specific model.
Fan Intermittent - Heating
| Indoor Unit Type | Intermittent Operating Time |
|---|---|
| Wall-mounted / Floor / Compact cassette | 3 min ON / 6 min OFF |
| Slim duct | 2 min ON / 6 min OFF |
| Other models | 1 min ON / 6 min OFF |
The heating intermittent-fan logic also changes with outside-air temperature. The bulletin shows a changeover with hysteresis around approximately 0-2°C outdoor temperature. Fan speed may be Quiet or Low depending on the selected airflow and indoor-unit type.
Applicable Australian R32 Models
Cassette
| Type | Models |
|---|---|
| Compact cassette | AUTH24KVLA |
| Circular flow cassette | AUTH24KRTA, AUTH30KRTA, AUTH36KRTA, AUTH45KRTA, AUTH54KRTA |
Ceiling
ABTH18KRTA, ABTH24KRTA, ABTH30KRTA, ABTH36KRTA, ABTH45KRTA, ABTH54KRTA
High Static Pressure Duct - Type 1
ARTH24KHTA, ARTH30KHTA, ARTH36KHTA, ARTH45KHTA, ARTH54KHTA, ARTH60KHTA
High Static Pressure Duct - Type 2
ARTH60KHTB, ARTH65KHTA, ARTH72KHTA, ARTH90KHTA
Other Applicable Markets
Europe:
- ARXH12KMTAP, ARXH14KMTAP, ARXH18KMTAP, ARXH22KMTAP, ARXH24KMTAP, ARXH30KMTAP, ARXH36KMTAP, ARXH45KMTAP, ARXH54KMTAP
- ARXH60KHTA, ARXH72KHTA, ARXH90KHTA
- AGEH09KVCCL, AGEH12KVCCL, AGEH14KVCCL, AGEH09KVCDN, AGEH12KVCDN, AGEH14KVCDN
Middle East:
- ARGH18CMTA-Q, ARGH24CMTA-Q, ARGH30CMTA-Q, ARGH36CMTA-Q, ARGH48CMTA-Q
- ARGH18CMTA-U, ARGH24CMTA-U, ARGH30CMTA-U, ARGH36CMTA-U, ARGH48CMTA-U
- ARGH60CMTA-Q, ARGH60CMTA-U
Service / Complaint Guidance
- Confirm whether the complaint occurs during thermo-off rather than while the system is actively heating or cooling.
- Confirm the indoor-unit model is one of the applicable R32 models.
- Check FS42, FS48 and the RC sensor setting to determine which room-temperature sensor is controlling the system.
- For Cooling/Dry, also check FS49 and the wired-controller energy-saving fan setting.
- For PAC heating applications, check FS43.
- If the fan stops during thermo-off with the wired remote controller selected as the active sensor, compare the setup with this bulletin before replacing components.
- Remember that thermo-on fan behaviour is unchanged by RAC-0131.