ErrorCodeDoctor
Daikin · Air Conditioner

Daikin Air Conditioner U9 error code

Difficulty: Hard · Cost: $80–$350 · Duration: Requires professional service

The U9 error means your Daikin air conditioner detected a transmission fault between units in another connected system. This can be caused by a defective electronic expansion valve on another indoor unit, a defective indoor unit PCB, or an improper connection in the transmission wiring. Contact a qualified technician.

Common causes

  • Transmission error between other indoor and outdoor units in the system
  • Defective electronic expansion valve of another indoor unit
  • Defective indoor unit PCB of another indoor unit
  • Improper connection of transmission wiring

How to fix it

  1. 1

    Contact a qualified technician to inspect the transmission wiring and expansion valves across all units in the system

Related Daikin Air Conditioner error codes

1

A0

An external protection device connected to the indoor unit has been activated

hard
2

A1

A fault was detected in the indoor unit PCB (control board)

hard
3

A3

The drain level control system has detected an abnormality — drain may be clogged

medium
4

A5

Freeze-up protection (cooling) or high pressure control (heating) has activated — check the air filter

easy