Daikin Mini-Split Error Codes: U, E, F, L, A

Quick Answer

Daikin mini-splits use a letter-number error code system where the letter prefix indicates the fault category: U codes (U0, U2, U3, U4, U9) cover communication faults and voltage issues between indoor and outdoor units over the 2-wire S1-S2 bus. E codes (E0, E3, E4, E5, E6, E7, E11) cover compressor protection, pressure limits, and motor faults.

Daikin's code system is actually pretty logical once you know the prefixes. U codes almost always mean something's wrong with the signal running between the two units. E codes are your compressor protection stuff. And honestly, the A3 drain clog shows up more than any other code I see on these units. Ignore these long enough and you're looking at a dead compressor or a flooded ceiling.

DaikinMinisplit

About These Daikin Minisplit Error Codes

OK so Daikin organizes their codes by letter prefix and that's actually useful once you know the system. U is communication and voltage, E is compressor stuff, F is sensors, L is inverter faults, and A covers drain and airflow. I was on three FTXM units last week and every single one came down to knowing which prefix pointed me to the right component first. Saves a ton of guessing.

Most Common Error Codes

Communication wire issues (U codes)40%

Low refrigerant or compressor faults (E codes)24%

Outdoor fan motor failure (E7)14%

Voltage supply problems (U2, U9)12%

Drain line clog (A3)10%

Symptoms You May Notice

The indoor unit's display is showing a code you've never seen before and the system just shut off mid-cycle on the hottest afternoon of the year.
You can hear the outdoor unit try to start, run for maybe 30-60 seconds, then shut back down over and over without ever settling into normal operation.
The indoor unit is blowing air but it's room temperature, not cold, and you can tell the compressor outside isn't actually kicking on.
Water is dripping from the indoor unit or from the ceiling around it, which usually means the A3 float switch tripped because the drain's completely backed up.
Unit worked fine yesterday, there was a thunderstorm last night, and now nothing responds to the remote and you've got a blinking light pattern you can't figure out.

Tools Required for Diagnosis

Phillips #2 screwdriverFlat-head screwdriver (small, for terminal block screws)Digital multimeterFlashlight or headlampNeedle-nose pliersShop vac (for A3 drain line clogs)Non-contact voltage tester

How to Identify Your Error Code

ComponentComponent Under Test

Expected Range9000–11000 ohms

ConditionIf Open (OL) or infinite, replace component.

Frequently Asked Questions

Where do I find the error code on my Daikin mini-split?

If your indoor head has a digital display, the code shows right there. But if it's just got an LED indicator, use your remote. Hold the Cancel button for five seconds while pointing it at the unit. First you'll hear a short beep, keep holding, and when you hear that long continuous beep, the code is on your remote's display. It's a hidden feature that most homeowners have no idea exists. Seriously, I've shown this trick to people who've owned their units for years and they're always surprised. The LED blink method works too but it's way easier to miscount.

Can I reset a Daikin error code without fixing the problem?

Yeah, you can clear it, but that's the bad idea approach. The control board threw that code because it detected something actually wrong. If you're dealing with an E5 high-pressure fault or an L5 code, the system is protecting the compressor from burning out. You reset it, it runs 20 minutes, trips again. You reset it again. Keep doing that and instead of a $150 capacitor repair you're looking at a $1,200 compressor replacement. The board's smarter than it looks. Listen to it.

Which Daikin error codes can I fix myself?

A3 is the big one for DIY. That's the drain clog code and nine times out of ten you can clear it with a shop vac on the drain line outlet or a cup of distilled vinegar in the drain pan to kill algae buildup. F codes from a loose thermistor connector are also pretty accessible if you're comfortable with a screwdriver and not scared of unplugging a small wire. But anything L or E is high-voltage inverter territory and refrigerant system stuff. Put the tools down and call someone who's EPA 608 certified.

How much does it cost to fix a Daikin U4 communication error?

If it's just a loose wire on the S1-S2 terminal block, you're basically paying for a service call, usually $80-150, and the tech spends five minutes tightening a screw. Best case scenario. If the communication board or the main PCB got fried by a surge, you're into $300-600 for parts plus labor. I swapped a control board on an FTXM12 last month, parts were $280 and it took about an hour. Still way cheaper than a new unit, and that's usually how I frame it for people.

My Daikin shows a U0 code. Is that a refrigerant problem?

U0 actually means the outdoor unit is detecting a voltage issue on the power supply side, not refrigerant. Check that your outdoor unit is getting the right voltage at the disconnect. It should be within 10 percent of the rated voltage on the nameplate. U0 can also show up if the power company's supply is sagging during a heat wave and voltage is dropping below spec. Worth watching the voltage at the disconnect over a few minutes with your meter. If it's dropping and recovering, that's a utility problem, not a unit problem.

What does F3 mean and can I replace the sensor myself?

F3 is the outdoor air thermistor, just a small temperature sensor that runs $15-30 depending on your model. The tricky part isn't the sensor itself, it's making sure you get the right part number. I've seen homeowners order the wrong thermistor and the resistance curve doesn't match, so the board still throws the code after the swap. Pull the full model number off the label inside the outdoor unit cover and match it exactly when ordering. The physical swap is simple, unplug the old one, plug in the new one. Just be careful not to kink or pinch the new wire when you're routing it.

Related Daikin Minisplit Error Codes

Code: U4Daikin U4: Communication Fault Code: E7Daikin E7: Outdoor Fan Motor Fault Code: A3Daikin A3: Drain Pan Overflow Code: U0Daikin U0: Low Refrigerant or Overcurrent Code: L5Daikin L5: Compressor Overcurrent

Models Known to Experience HUB Errors

This repair applies to most Daikin minisplits with this error code. Common model numbers include:

FTXS09LVJU, FTXS12LVJU, FTXS15LVJU, FTXM09QVJU, FTXM12QVJU, FTXM15QVJU, FTXM18QVJU, FTXM24QVJU

Written by

Raj Patel

HVAC & Water Systems Specialist · 15 years experience

Last verified for technical accuracy on March 15, 2026