Fujitsu Mini-Split: 13 Flashes
Code J2: Branch box error
Soft lockoutShown as: OPERATION lamp blinks 13 times, TIMER lamp blinks 2 times, ECONOMY lamp blinking continuously
Branch box error. The branch box has stopped communicating with the indoor units connected to it.
Manual wording: “Branch Box Error - When the branch box stops communicating with connected indoor units.”
Documented for: Halcyon HFI Flex multi-zone systems with branch boxes (RLF/RLF1 indoor units, RLXFZ outdoor units); AOU48RLXFZ shows EJ2U
Likely causes, most common first
- Loose or erroneous molex plug connections in the branch box
- Defective or crossed field wiring between the branch box and the indoor units
- Branch box lost power
- Failed branch box control board
What you can safely check yourself
- Check that the branch box still has power at its breaker
- Turn the power off to the outdoor unit and branch boxes for about 5 minutes, then restore power
When to call a technician
Branch box wiring runs at line voltage and every zone lands there. Have the installing contractor trace and correct it.
A Fujitsu mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- 410A Mini-Split Troubleshooting Guide (Part # 6-26-FG2020 Rev. 5/2019) (Fujitsu General America, Inc., All R410A Halcyon mini-splits: RGLX, RL2/RLS3/RLS3H/RLS3Y/RLB/RLXB/RLXEH wall mounted, RLF/RLF1 multi-zone indoor units, RLXFZ multi-zone outdoor units, RML/RMLQ, RULX/RSLX universal-mount, RCLX cassettes) · checked 2026-08-25