Daikin U8 error code

What it means

U8 means two controllers or a controller pair are not agreeing as main/sub or are not communicating normally.

Urgency

Likely causes

1. Brief power event, brownout, or unstable supply voltage
2. Loose power connection, reactor, or outdoor electrical component problem
3. Inverter/IPM protection or current-detection fault
4. Compressor winding, drive, or outdoor board fault after power checks pass

Homeowner fix

Do not change installer settings. Power cycle once if safe; if U8 returns, note whether there are two controllers and call for service.

When to call a pro

Call a licensed HVAC technician if U8 returns. Tell them the code is main/sub remote-controller transmission.

Repair vs replace

Sensor and communication faults are usually repairable. Compare repair with replacement only if the system is older, out of warranty, or multiple boards or sensors are being quoted together.

• Daikin AURORA 9,000 BTU R-32 208/230V (FTXV09AVJU9 / RXT09AVJU9)

  AURORA R-32

• Daikin AURORA 12,000 BTU R-32 208/230V (FTXV12AVJU9 / RXT12AVJU9)

  AURORA R-32

• Daikin AURORA 15,000 BTU R-32 208/230V (FTXV15AVJU9 / RXT15AVJU9)

  AURORA R-32

• Daikin AURORA 18,000 BTU R-32 208/230V (FTXV18AVJU9 / RXT18AVJU9)

  AURORA R-32

Parts for this line

The parts catalog for Daikin AURORA R-32 lists 7 sourced replacement parts for this product line.

For your technician

Technician note: verify main/sub controller settings, controller compatibility, wiring, and indoor controller communication. Page context: Daikin maps this display to the AURORA R-32 line; source: Daikin Nineteen, ATMOSPHERA, Entra, and MXM/MXT/MXTH local service manuals; display convention: match the letter U and eight marker exactly before comparing neighboring codes.

Which systems show it

• Daikin current US residential R-32 ductless single-zone systems, including AURORA R-32, ATMOSPHERA R-32, Entra R32, OTERRA R-32, and Nineteen-series style high-wall diagnostics where the same Daikin A/C/E/F/H/J/L/P/U code family is used.
• Daikin concealed-duct/FDMQ indoor units where the Nineteen service manual explicitly lists the same indoor drain, fan PCB, remote-controller, and FDMQ-only C/U codes.
• Daikin AURORA Multi R-32 and Standard Multi R-32 MXT/MXTH/MXM systems where the MXM engineering manual lists the same homeowner code table.
• MXM/MXT/MXTH multi-zone systems for the additional multi-zone U-series and inverter/control codes specifically called out from the MXM manual.

Related troubleshooting

Use the symptom guide alongside the exact display code if the unit is flashing, cycling, or showing comfort symptoms.

Reset note

Do not change installer settings. Power cycle once if safe; if U8 returns, note whether there are two controllers and call for service.

Manual trigger

U8 means two controllers or a controller pair are not agreeing as main/sub or are not communicating normally.

Related codes

Source

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