Daikin U4

High

VRV / Sky Air — Transmission error indoor/outdoor unit.

Daikin U4: Transmission error indoor/outdoor unit. This fault noticeably affects operation.

Possible causes

Faulty/loose interconnect wiring.
Noise interference.
Indoor or outdoor PCB faulty.

Check steps

Check F1/F2 wiring & polarity.
Check shielding/routing.
Clears on reset: often transient.

Affected parts

Verbindungsleitung
PCB

Safety note

230V — isolate power.

Source: Daikin SM-TS3 (Simple Self-Diagnosis by Malfunction Code, resmi) veya VRV IV+ Service Manual (ManualsLib) — SM-TS3 p.5: 'U4 Malfunction of transmission between indoor and outdoor unit — Short circuit in indoor-outdoor or outdoor-outdoor transmission wiring (F1/F2), or wrong wiring, Outdoor unit power supply is OFF, System addr

Reviewed by Anıl Güzeldemir — in the refrigeration machine room since 2006, developer of Enthalio.

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