. Purpose

This procedure allows verification that indoor units (IUs) are correctly wired and communicating with the outdoor unit (OU) on a Fujitsu AIRSTAGE VRF system. It confirms that all IUs are detected and correctly addressed before commissioning.

2. Equipment Overview

Outdoor Unit Interface

Located on the outdoor unit printed circuit board (PCB):

  • LED105 / LED104: Dual 7-segment LED display

  • LED101 (Green): Power indicator

  • LED102 (Red): Error indicator

  • Push-button switches:

    • SW107 – MODE/EXIT

    • SW108 – SELECT

    • SW109 – ENTER

These switches are used to navigate diagnostic and commissioning modes.

3. Preparation

Before running the connection test:

  1. Ensure all indoor units are powered ON but turned OFF at the controller.

  2. Verify wiring polarity and ensure transmission cables (X1/X2) are correctly terminated.

  3. Ensure the outdoor unit is powered and operational (LED101 illuminated green, no active error light).



4. Accessing the Connection Check Mode

Step-by-Step Procedure

Step 1 – Enter Function Mode

  1. Press the MODE/EXIT (SW107) button once.
    → The display will show F0.

Step 2 – Select Function Code

  1. Press the SELECT (SW108) button twice.
    → The display will change to F3.

Step 3 – Confirm Function

  1. Press the ENTER (SW109) button once.
    → The display will show 00.

5. Running the Indoor Unit Connection Check

Step 4 – Select Function Number

  1. Press the SELECT (SW108) button repeatedly until the display shows 12.
    → This corresponds to the Indoor Unit Connection Test.

Step 5 – Start the Test

  1. Press the ENTER (SW109) button once.
    → The display will change to run, indicating the system is checking communication.



6. Interpreting Results

After the system completes the check, the display will show one of the following:

DisplayMeaningAction Required
PASSAll indoor units successfully recognizedProceed to commissioning
FAILOne or more indoor units not recognizedEnsure all indoor units are powered ON but OFF at controllers, then re-run test
ErrCommunication or wiring error detectedCheck transmission cable connections, address conflicts, or contact Fujitsu Technical Support
U01, U02, etc.Displays number of connected indoor unitsIndicates number of successfully detected indoor units

Tip: If “FAIL” occurs, power cycle both indoor and outdoor units and confirm address settings before repeating.

7. Exiting Connection Check Mode

To exit and return to normal operation:

  • Press the MODE/EXIT (SW107) button twice.

  • The LED display will clear.

8. Troubleshooting Summary

SymptomPossible CauseRecommended Action
FAIL displayedIndoor unit powered OFF or miswiredConfirm power and wiring to each IU
Err displayedFault on transmission lineCheck polarity and continuity on X1/X2
U01 or low unit countMissing units in system mapVerify address duplication or broken network
No displayOutdoor PCB not poweredCheck main supply and fuse
LEDs not respondingButton fault or PCB issueContact technical support

9. Key Notes

  • Always perform this test after addressing and before system operation.

  • Run the check one refrigerant system at a time to avoid cross-communication.

  • The test does not run if the indoor units are ON at the controller—they must be in standby.

  • Document results as part of the pre-commissioning verification report.