Equipment
- Daikin 18,000 BTU ductless heat pump (outdoor unit RXB18AXVJU, R-410A, built in 2018), the smaller of two systems in the home
Daikin mini split fan motor and control board replacement in Concord
Problem: This Concord home has two Daikin ductless heat pumps, and the smaller one quit. Pressing the remote got a blue light on the indoor unit and nothing else. The remote showed U4. On a Daikin mini split, U4 means the indoor and outdoor units have stopped talking to each other.
Diagnostics: The outdoor unit is a Daikin RXB18AXVJU, an 18,000 BTU heat pump built in 2018. On the first visit our technician found a blown 3.15 amp slow-blow fuse. A fuse like that usually blows because something behind it pulled too much current, so a new fuse alone often isn’t the fix.
Solution: We replaced the outdoor fan motor first. Testing after the new motor went in pointed to the main control board. On October 19 we came back and replaced the control board.
Result: The outdoor unit now has a new fan motor and a new control board. If your mini split shows U4, check the breaker for the outdoor unit first. If the power is on and the code keeps coming back, the cause could be a fuse, a failing part that took the fuse out, a board, or the wiring between the units.
We repair Daikin mini splits in Concord, CA and across the East Bay. See our mini-split repair service.
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