Daikin Mini Split U8 Error Code

Updated 2026-08-29 · review status: manual-verified · reviewed by MiniSplitDecoder Editorial Team Last verified: 2026-08-29

Check your model first

The source record does not specify an exact model family.

Match the model on your equipment label to the linked manufacturer documentation. The same code can mean different things across model families.

Quick answer

U8 means transmission between remote controllers (main-sub wired controllers) has failed. Check the wiring between the units/controls and power cycle once; if the code returns, the transmission circuit needs a technician.

Severity: medium · DIY difficulty: intermediate

Safety

Stop at visual wiring checks and one reset. Do not disconnect live wiring or open controller/PCB housings - transmission-circuit diagnosis is technician-only.

What U8 means

U8 means transmission between remote controllers (main-sub wired controllers) has failed - the wired transmission between the components cannot be trusted, so the system stops to protect control integrity.

Causes, ranked

  1. 1. Wiring damage, loose terminal, or wrong connection between the components common DIY

    Check: Visually check the interconnecting cable at both ends for damage or loose strain relief (do not disconnect live wires).

    Fix: If damage is visible, schedule service; otherwise power cycle once and retest.

  2. 2. Transient protection event that clears after one reset common DIY

    Check: Power cycle once at the breaker and run the unit through a full cycle.

    Fix: If the code does not return, monitor; if it returns, stop resetting and schedule service.

  3. 3. Electrical noise from nearby power equipment on the transmission line occasional pro only

    Check: Requires routing inspection and noise measurement.

    Fix: Technician: re-route the transmission wiring away from power lines, add shielding.

  4. 4. PCB transmission-circuit fault after wiring is verified rare pro only

    Check: Board-level diagnosis only.

    Fix: Technician: diagnose the PCBs; replace the faulty board.

Related codes

Cross-references for the same fault family, by brand:

Daikin U5 · Daikin U9

Commonly searched as: "daikin u8" · "daikin error code u8" · "daikin air conditioner u8"

Sources

Related Mini Split guides

Mini-Split Communication Error: DIY Checks · Mini-Split Flashing Light Decoder: Blink Patterns · How to Reset a Mini-Split After a Power Outage