Daikin U0 Error Code: Refrigerant shortage
Updated October 2026 · Sourced from Daikin documentation
The system detects a refrigerant shortage by checking the input current and compressor running frequency, the discharge pipe temperature and expansion valve opening, or the suction and discharge temperature difference.
Is it safe to keep running? No. Turn it off and get it checked. Refrigerant work must be done by a licensed technician. Do not try to add or handle refrigerant yourself.
U0 at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| U0 Shown on the remote controller (and as blinking lamps on the indoor unit) | Refrigerant shortage | Daikin FTXS-L / FDXS-L inverter pair ductless series (09 to 36 class, models FTXS09-36LVJU, FDXS09-12LVJU) |
Check this first
Only steps a homeowner can do safely. Do not open electrical panels or the burner area.
- Turn the system off until it is serviced.
🛑 Stop and call a licensed pro if
- Refrigerant work must be done by a licensed technician. Do not try to add or handle refrigerant yourself.
- Any code pointing to refrigerant, the compressor, high pressure or the outdoor unit board. Refrigerant work legally needs a certified technician.
- Burning smell, sparks, or a breaker that trips again after a reset.
- Water leaking from the indoor unit that does not stop after the drain is clear.
Safe first steps for any Daikin code
- Write down the exact code and how it shows (remote display or number of lamp blinks). Similar codes mean different things on different series.
- Turn the system off at the remote, switch off the breaker or disconnect for the unit, wait a few minutes, then turn it back on.
- Clean or replace the indoor unit air filters, and make sure nothing blocks the indoor or outdoor unit.
- Check that the condensate drain line is not blocked or kinked where you can see it.
- Replace the remote controller batteries if the display is dim or the unit does not respond.
Source: Daikin Service Manual SiUS091133 - FTXS-L / FDXS-L Series, Troubleshooting p.104. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.
Shaun Cain · Certified HVAC & Refrigeration Technician · Ask an HVAC technician