Daikin Error Codes: What Each Code Means and How to Read It

Daikin error codes are a letter and a number, such as U4 or A5, that you read on the wireless remote when the indoor unit's OPERATION lamp keeps blinking. Hold the remote's TIMER CANCEL button for 5 seconds, then press it again and again until the unit gives a long beep: the code on the remote at that moment is the fault. Daikin's first owner step is to clean the filters, clear the air inlets and outlets, switch the breaker off and on, and restart from the remote.

How to read a Daikin error code with the remote

The indoor unit blinks its OPERATION lamp, and the remote finds the code by trial: you step through codes until the indoor unit beeps to confirm a match. The FTXS LV Series operation manual gives these steps for its ARC452A remote:

1. Hold the TIMER CANCEL button for 5 seconds. "00" flashes in the temperature area of the remote.
2. Press TIMER CANCEL repeatedly. The code on the remote changes with each press.
3. A short beep followed by two quick beeps means that code is not the fault. Keep pressing.
4. A continuous, long beep means the code now on the remote is the fault. Write it down.
5. To leave the code display, hold TIMER CANCEL for 5 seconds. It also cancels itself after 1 minute without a press.

Remotes with separate ON TIMER CANCEL and OFF TIMER CANCEL buttons, such as the BRC52A and BRC52B, work the same way with either button. Daikin's service manual for the FTXB and FTXN wall units adds that two quick beeps mean either the letter or the number is right. On those units the indoor LED blinks blue for any error, and the blink pattern itself does not tell you which one.

On the current Aurora models (FTX09, FTX12 and FTX15WMVJU9), the button is labeled CANCEL. The Aurora operation manual says a blink about every 0.5 seconds means a fault, and tells you to point the remote at the indoor unit while you press CANCEL. One beep means no match, and a long beep means the code is the fault.

What Daikin tells you to do first

The LV Series manual's "Check again" table gives the owner steps for a unit that stopped with the OPERATION lamp flashing:

1. Clean the air filters if they are dirty.
2. Check that nothing blocks the air inlet or outlet of the indoor or outdoor unit.
3. Turn the breaker off, take away any obstacle, turn the breaker back on and start the unit with the remote.
4. If the lamp still flashes, call the service shop that sold you the unit.

The same manual says lightning or radio waves can make the unit misbehave, and the fix is the same breaker off and on. After a power failure, the unit restarts by itself in about 3 minutes. If the remote display is dim or blank, replace all its batteries with new AAA alkaline cells. Our guide to resetting an air conditioner walks through a safe power cycle.

Stop the unit, turn the breaker off and call the service shop if the power cord is hot or damaged, you smell burning, you hear abnormal sounds, the breaker trips often or water leaks from the indoor unit.

Daikin error code table

Codes from two Daikin documents: the FTXS LV Series operation manual (FTXS30HVJU, FTXS36HVJU, FTXS30LVJU and FTXS36LVJU, ARC452A remote) and the service manual for the FTXB, FTKB, FTXN and FTKN AXVJU wall units, which Daikin files under its 17 Series. Where the two manuals list a code differently, the meaning says which series it is from. Every code and meaning is Daikin's. The owner steps are only those Daikin's manuals give.

"Clear the outdoor unit" means the step Daikin gives for a flashing lamp: breaker off, take away anything blocking the outdoor unit's inlet or outlet, breaker on, restart.

The BRC52B handset manual prints a longer list that covers other Daikin systems, with codes such as A3 (drain pump abnormal), J1 (pressure sensor error) and UF (piping and wiring mismatch). If your remote lands on a code that is not in the table above, look it up there.

U4: the indoor and outdoor units are not communicating

U4 is one of the codes owners see most. Daikin's manuals call it a failure of transmission between the indoor and outdoor units. Try the breaker off and on once and restart from the remote. If U4 comes back, the FTXB and FTXN service manual lists the causes: a faulty indoor or outdoor circuit board, a wiring error or broken wire between the units, or a disturbed power supply. All of those need a licensed HVAC technician.

U0: refrigerant shortage

U0 means the system reads as short of refrigerant. The FTXB and FTXN service manual lists a refrigerant leak, a closed stop valve, a disconnected sensor, a weak compressor or a faulty expansion valve as causes. There is no owner step for any of them. Turn the breaker off and contact your dealer or a technician, which is what the Aurora manual says to do when a code repeats. Poor cooling without a code has other causes, which our guide to a heat pump that is not cooling covers.

A5: freeze-up or high pressure protection

A5 means the indoor coil got too cold in cooling or too hot in heating, so the unit protected itself. The FTXB and FTXN service manual lists the likely causes, and the first one is something you can fix: an indoor air filter or heat exchanger blocked by dust. Clean the filters, check that nothing blocks the indoor unit's air inlet or outlet, then restart. The other causes in the manual, a faulty coil sensor, circuit board or dirty fan blower, are for a technician.

E7, L3, L4 and L5: the outdoor unit is the problem

The Aurora manual gives owner steps for these. E7 means the outdoor fan has stopped. Check for a foreign object inside the outdoor unit. Turn the breaker off before you remove it, then turn the power back on and run the unit.

L3, L4 and L5 mean the inside of the outdoor unit got too hot and the unit stopped. Check whether something blocks the outdoor unit's air outlet. Turn the breaker off, clear it, restore power and run the unit.

In both cases, Daikin says that if the OPERATION lamp stays lit without blinking after the unit runs for a while, carry on as normal. If it starts blinking again, turn the breaker off and contact your dealer.

Which Daikin models this page covers

The table and steps come from Daikin's own US documents, opened in October 2026:

• Operation manual for FTXS30HVJU, FTXS36HVJU, FTXS30LVJU and FTXS36LVJU (LV Series wall mount), with the ARC452A remote.
• Service manual SM-5WM-Y-NA-B1 for FTKB, FTXB, FTKN and FTXN 09, 12, 18 and 24AXVJU indoor units and their RKB, RXB, RKN and RXN outdoor units, with the BRC52A and BRC52B remotes.
• The BRC52B wireless handset operating manual (OM-BRC52B-0617).
• Operation manual for the Aurora FTX09, FTX12 and FTX15WMVJU9. The copy we opened has only its French section, so the E7 and L3 to L5 steps above are our translation.

This page covers the wall-mounted units listed above, not Daikin's ducted or VRV systems. For a different model, find its operation manual by model number on daikincomfort.com. Note that Daikin's E8 is an input over-current fault, not the fan fault our general E8 error code guide describes. If you own a MrCool, our MrCool error codes page has that brand's list.