The U4 error code could mean the indoor and outdoor units can’t communicate with each other over the interconnecting wiring that links them. This is one of the most commonly seen Daikin fault codes, and it usually points to something in that wiring connection rather than a major component failure.
Because the indoor and outdoor units rely on this link to coordinate their operation, a communication fault will typically stop the system running altogether until it’s resolved.
Send us the code and a photo of the display, and a Ford & Doonan technician will get back to you. Please don't reset the unit before you take the photo.
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