Daikin Heat Pump Error Code U8

U8Daikin Heat Pump

What this code means

Signal transmission error between MAIN remote controller and SUB remote controller – normal transmission does not continue for specified period.

First step from the service manual

Check if the remote controller is set to MAIN when using 1 remote controller; if set to SUB, change to MAIN.

Next steps: diagnose the root cause

1
Verify the error code is active

Power cycle the unit and see if the code returns. If it does, the fault is persistent and requires diagnosis.

2
Get the full diagnostic procedure

Get step-by-step guidance, test values, and wiring diagrams from the OEM service manual.

Start diagnosing U8 on your Daikin heat pump

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What’s available for Daikin heat pump models

Access Daikin heat pump service manuals, wiring schematics, exploded parts views, and error code references on MyPros+.

Related Daikin heat pump error codes

00Normal operation, no fault detected.A1Indoor unit PCB abnormality; the system cannot set the internal settings.A3Drain level control system abnormalityA5Freeze-up protection control (cooling) or heating peak-cut control (heating)…A6Indoor fan motor (DC motor) or related abnormality; detected rotation speed…AFHumidifier or related abnormalityC4Indoor heat exchanger thermistor 1 (liquid pipe) (R2T) or related abnormalityC5Indoor heat exchanger thermistor 2 (R3T) or related abnormalityC7Front panel open/close fault.C9Room temperature thermistor (R1T) or related abnormalityCEPresence sensor or floor sensor abnormalityCJRemote controller thermistor abnormalityE1Outdoor unit PCB abnormalityE5OL activation (compressor overload)E6Compressor lockE7DC fan lock (outdoor fan motor)E8Input overcurrent detectionEAFour way valve abnormalityF3Discharge pipe temperature controlF6High pressure control in coolingF8System shutdown due to compressor internal temperature abnormalityH0Compressor system sensor abnormality; DC current voltage before compressor…H6Position sensor abnormalityH8DC voltage/current sensor abnormality identified based on compressor running…H9Outdoor temperature thermistor or related abnormalityJ3Discharge pipe thermistor or related abnormality; discharge pipe temperature is…J6Outdoor heat exchanger thermistor or related abnormalityL3Electrical box temperature riseL4Radiation fin temperature riseL5Output overcurrent detectionP4Radiation fin thermistor or related abnormality.U0Refrigerant shortage detected.U2Low-voltage detection or over-voltage detectionU4Signal transmission error between indoor unit and outdoor unitU5Signal transmission error between indoor unit and remote controllerUAUnspecified voltage between indoor unit and outdoor unit; pair type and multi…
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