U3 is the Daikin code most likely to appear right after someone worked on your system, and it is usually less alarming than it looks.
What U3 means
Daikin U3 indicates that check operation was not executed, or a transmission error occurred during it. Check operation is the commissioning routine a technician runs after installation or major work: the system verifies its own piping, wiring and refrigerant setup. If that routine was skipped or interrupted, the unit flags U3. Medium severity in the Daikin table, see our Daikin error codes guide.
What usually causes U3 in Singapore
The single most common cause we see is a rushed installation where the installer never ran check operation at all, either because they did not know how or because they were racing to the next job. It can also appear after a repair or a board replacement, or when a communication issue interrupts the routine mid way.
Why it matters more than it looks
U3 itself is not damaging your unit. But it is a receipt: it tells you the commissioning step was skipped, and that step is what catches piping and refrigerant mistakes before they become expensive. If your system is new and showing U3, that is worth a conversation with whoever installed it.
What our technician does
Run check operation properly and read what it reports. That routine often surfaces the real underlying issue, and clearing U3 without running it is just hiding the light.
What it costs
Usually a single service visit. If check operation then reveals an installation fault, we will show you exactly what it found before quoting anything further. Diagnosis rates are on our aircon repair in Singapore page.
U3 showing right now?
WhatsApp +65 8818 5781 with your model number and a photo of the display. We will tell you honestly whether it is a quick fix, a repair worth doing, or nothing to worry about. Our aircon repair in Singapore service covers every brand with published rates and a 30 day labour warranty.
