Daikin Air Conditioner Error Code UA

The UA code on a Daikin air conditioner signals a system configuration fault, specifically that either too many indoor units are connected to the outdoor unit, or the indoor and outdoor units are using incompatible refrigerant types. The outdoor unit PCB detects this mismatch and halts normal operation. This error commonly appears after an outdoor unit PCB replacement or after a system expansion where an additional indoor unit was added.

A simple power reset will not permanently clear the UA error because it is caused by an underlying configuration issue, not a temporary fault. The system will re-detect the same incompatibility and trigger UA again after restarting. The root cause, whether it is an excess number of indoor units, a mismatched refrigerant type, or a newly installed PCB, must be resolved before the error will clear.

The cost depends entirely on the root cause. If the fix involves only reconfiguring settings or correcting wiring, the expense may be limited to a service call fee, typically in the range of $75 to $200. If a new outdoor unit PCB is needed, parts and labor combined can range from $300 to $800 or more depending on the model and your location. A technician will need to diagnose the specific cause before an accurate estimate can be provided.

Diagnosing UA requires checking the outdoor unit PCB, counting connected indoor units against the rated capacity, and verifying refrigerant type compatibility across all units. These steps involve accessing control boards and system wiring, which should be handled by a qualified HVAC technician. If the fault is simply due to an incorrect unit count or an address setting error, a technician may be able to resolve it without replacement parts.

The UA error code causes the system to suspend normal operation, so the unit will not run in its standard cooling or heating mode while the fault is active. Attempting to force operation in this state is not recommended, as the underlying configuration mismatch could cause improper refrigerant handling or damage to system components. The fault should be diagnosed and corrected before returning the system to service.