Daikin Heat Pump Error Code UA

The UA error code indicates that there is an unspecified voltage condition between the indoor and outdoor units caused by an incompatible unit pairing. Daikin heat pumps detect when a pair-type indoor unit is connected to a multi-type outdoor unit, or when another mismatched combination is in use. The system will not operate normally until compatible units are connected. A technician must verify the model numbers and system types of both units to resolve this fault.

Resetting the unit will not clear the UA error code if the underlying cause is an incompatible indoor and outdoor unit combination. The fault will return immediately upon startup because it reflects a fundamental system configuration problem. The error will only clear permanently once the correct compatible units are connected and the system recognizes a valid pairing.

If the error is caused by incorrect wiring, repair costs are generally limited to a service call fee, typically in the range of $75 to $150 depending on your location. If the indoor or outdoor unit must be replaced due to an incompatible model pairing, costs will increase significantly and depend on the unit type and size required, with equipment and installation potentially ranging from several hundred to several thousand dollars.

The first step you can take is to locate the model numbers on both your indoor and outdoor units and confirm they are a compatible pair. However, if the units are determined to be incompatible, resolving the issue requires replacing one of the units with the correct model, which is work that should be performed by a licensed HVAC technician. Incorrect wiring is another potential cause that a technician should inspect and correct.

The system will generally not operate normally while the UA fault is present, as it is designed to prevent operation when an incompatible unit combination is detected. You should not attempt to override or bypass this fault. Leaving incompatible units interconnected can place abnormal stress on the control boards and wiring, so the issue should be addressed before attempting to use the system.