Daikin Air Conditioner Error Code U8

U8 indicates a communication error between the main remote controller and one or more sub remote controllers in a multi-controller setup. The system detected that the expected communication signal was absent or abnormal for an extended period. This error causes the unit to stop normal operation until the communication issue is resolved.

A simple power reset will not permanently clear U8 if the underlying cause has not been addressed. The fault will return as soon as the system attempts to re-establish communication between the controllers and finds the same problem. The SS-1 switch configuration and wiring must be corrected first.

If the fault is caused only by an incorrect SS-1 switch setting, a service call to diagnose and correct the configuration typically costs between $75 and $175 depending on local labor rates. If wiring repairs or a replacement remote controller circuit board are required, costs can range from $150 to $500 or more depending on parts pricing and the complexity of the repair.

Start by locating the SS-1 switch on each remote controller installed in the system. Confirm that exactly one controller has its SS-1 switch set to MAIN and all others are set to SUB. If the switch settings are already correct, inspect the communication wiring between the controllers for loose terminals, damage, or reversed polarity.

U8 is a communication fault rather than a refrigerant, electrical, or safety hazard. The system stops operating to protect against undefined control behavior, but there is no immediate danger to the home or occupants. The unit should be serviced promptly to restore normal operation, but U8 does not represent an urgent safety emergency.