Daikin Mini-Split Code U8
Warning
Signal transmission error between the MAIN remote controller and the SUB remote controller.
Manual wording: “U8 Signal transmission error between MAIN remote controller and SUB remote controller”
Documented for: Systems with two wired wall remote controllers on one indoor unit
Likely causes, most common first
- Remote controller is set to SUB when only one controller is used
- Connection of two SUB remote controllers
- Defective remote controller PCB
What you can safely check yourself
- Turn the system off at the breaker or disconnect switch, wait a minute, and turn it back on once
When to call a technician
The MAIN/SUB setting lives inside the wall controller. Have a technician set it correctly.
A Daikin mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- Service Manual - Multi-Split Type Air Conditioners RMXS-L Series (SiUS181631EA) (Daikin, RMXS48LVJU outdoor, BPMKS048A2U/049A3U branch provider, CTXG/CTXS/FTXS/CDXS/FDXS/FVXS/FFQ indoor units) · checked 2026-08-25