Daikin U2 Error Code: Low-voltage or over-voltage detection
Updated October 2026 · Sourced from Daikin documentation
The indoor unit found no power supply zero-cross detection for about 10 seconds, or the outdoor unit detected an abnormal voltage drop or rise. The compressor stops and restarts automatically after a 3-minute standby.
Is it safe to keep running? Check the steps below first. If it repeats, a licensed technician or electrician should check the supply voltage and the unit board.
U2 at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| U2 Shown on the remote controller (and as blinking lamps on the indoor unit) | Low-voltage or over-voltage detection | 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.
- Switch the unit off at the breaker, wait a minute, then switch it back on and see whether the code returns.
- If other appliances on the same circuit act up, mention that to the electrician or technician.
🛑 Stop and call a licensed pro if
- If it repeats, a licensed technician or electrician should check the supply voltage and the unit board.
- 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.107. 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