Daikin mini split error code U0
Refrigerant shortage.
- TypeFault
- SystemRefrigerant circuit
- Can I fix it?Homeowner checks, then maybe a tech
What U0 means on a Daikin
The outdoor board concluded from temperatures and pressures that the refrigerant charge is low. On a new installation this points to a flare joint that did not seal or a service valve left closed; on an older system it means a leak. U0 is one of the most common Daikin codes.
On this platform, U0 is a fault: something has failed or is disconnected and needs diagnosis.
Common causes
- A leaking flare joint.
- Service valves not fully open.
- An incomplete charge at installation (long line sets need extra refrigerant).
- A genuine leak in the coil or piping.
How to fix it yourself
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician.
- Open both service valves fully.
- Leak-check every flare joint with soapy water while the system runs.
- Pull the front panel and check the filters and the indoor coil. Dirty filters and a matted coil restrict airflow, and airflow problems trigger a surprising number of protection codes.
- Anything inside the refrigerant circuit (sensors are fine, but valves, compressors and leaks are not) needs EPA-certified refrigerant handling. That is a technician job.
Switch off power at the breaker before opening either unit. Capacitors in the outdoor unit hold a charge for several minutes after power is cut.
When to call a technician
A technician must find the leak, repair, evacuate and recharge by weight. Do not just top it up.
Which Daikin units show U0
This page applies to Daikin Aurora, 19 Series, Atmosphera, Emura, Quaternity and MXS multi-zone units. Daikin's own documentation lists U0 as "Refrigerant shortage", the same definition used across the Daikin it is built on. If your unit shows a code with a different shape (for example a four-character code, or a plain number), it is from a different table; use the lookup with your exact code.
Where Daikin shows this code
Most Daikin wall units do not show the code on the unit; the operation lamp blinks. To read the code, point the remote at the unit, hold CANCEL (or Timer Cancel) for about 5 seconds until 00 shows, then press CANCEL repeatedly. Each press shows a code; when the unit gives a long continuous beep instead of two short beeps, the code on the remote is the stored fault. Units with a wired controller show the code directly. A and C codes are indoor-unit faults, E, F, H, J, L and P codes are outdoor-unit faults and protections, and U codes are system-level problems such as communication, power supply and refrigerant shortage.
Other Daikin codes
Same part of the system as U0:
U0 on other brands
The same characters do not always mean the same thing. Check the brand on your unit.
- Goodman U0 Refrigerant shortage
Questions people ask
Can I reset a Daikin U0 code myself?
Yes. Turn the system off at the breaker for five minutes, then restart it. If U0 comes back, the fault is real and needs the checks above.
Is it safe to keep running a Daikin showing U0?
The unit will usually refuse to run, or run with reduced output, until the fault is cleared. Repeated resets do not fix anything and can mask a problem that is getting worse.
Do I need a technician for Daikin U0?
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician. A technician must find the leak, repair, evacuate and recharge by weight. Do not just top it up.
Sources
- Daikin residential (RA) service manuals (error code tables)
- Daikin operation manuals (remote controller self-diagnosis)
Updated September 2026. Codes and definitions vary by model year. If your manual disagrees with this page, your manual wins. Send a correction.