Daikin | Fan Coil

Error Code U4

Troubleshooting guide for the Daikin Fan Coil system fault U4.

Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.

System Diagnosis

Malfunction of transmission between indoor and outdoor unit

Potential Causes & Solutions

  • Short circuit in indoor-outdoor or outdoor-outdoor transmission wiring (F1 / F2), or wrong wiring.
  • Outdoor unit power supply is OFF.
  • System address does not match.
  • Defective indoor unit PCB.
  • Defective outdoor unit PCB.

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