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Causes & Recommended Solutions

The U4 error code means a communication failure between the indoor and outdoor units. This can result in a loss of control or total system shutdown.

Common Causes of the U4 Error Code

Disconnected Communication Wires

Broken or unplugged communication cables.

Mismatched System Components

Incompatible units or misconfigured control systems.

Interference or Electrical Noise

External electrical interference disrupting the signal.

Recommended Solutions

Inspect Communication Wiring

Ensure all communication cables are properly connected and undamaged.

Check Compatibility

Verify that all connected units are compatible and configured correctly.

Reduce Interference

Minimize nearby sources of electrical noise or shield the wiring.

Need Expert Help?

Call Skycon Air Conditioning!

If you’ve tried these steps and the issue persists, don’t risk further damage. At Skycon Air Conditioning, our expert technicians specialize in mitsubishi-electric- air conditioner repairs and can diagnose & fix the problem quickly.
1300 264 424
1300 264 424