Daikin Mini-Split Error Codes: What Each Code Means and What to Do

Daikin mini-splits display error codes on the indoor unit’s front panel and on the remote controller when a fault is detected. The codes group into four categories that tell you which system is involved:

• A-codes: protection devices activated (drain safety, indoor PCB, freeze protection)
• C-codes: sensor faults (temperature sensors, remote sensor)
• E-codes: outdoor unit protection (high pressure, low pressure, compressor, outdoor fan)
• U-codes: communication errors, power supply faults

Most A-codes and some U-codes have DIY-accessible first steps. E-codes and C-codes almost always require a technician with diagnostic tools and refrigerant handling certification.

Your installation manual is the T0 authority. Daikin sells multiple product lines and code assignments vary between them. Find your model number (on the nameplate inside the indoor unit’s front panel, behind the filter) and confirm codes in the manual.

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How to access Daikin error codes

Current fault: the code appears on the indoor unit display or remote controller display. Some units show it as a scrolling alphanumeric sequence.

To view stored fault history: on units with a more advanced controller, press and hold certain buttons on the remote to enter diagnostic mode. The specific button combination varies by remote — consult your manual’s “Diagnostics” or “Fault History” section.

To clear and reset: turn the unit off from the remote. Wait 3–5 minutes. Turn it back on. If the fault is resolved, the unit will run normally. If the condition is still present, the code returns.

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Common Daikin mini-split error codes

A0 — Protection device activated (indoor)

A general indoor protection device has triggered. This is a catch-all fault indicating the unit stopped to protect itself from an abnormal condition. Can relate to electrical surge protection, temperature limits, or other indoor safety inputs.

What to try: power off for 5 minutes, power on. If A0 returns immediately or recurs repeatedly, call a tech — the protection device may have tripped due to a real electrical or refrigerant condition.

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A1 — Indoor unit PCB (control board) fault

The indoor unit’s main control board has detected an internal fault. Board-level faults are not homeowner-serviceable. This error typically requires a technician to test the board and replace if confirmed failed.

Possible causes:

• Power surge damage to the board
• Firmware error on the board
• Loose ribbon connector between board and display

If you recently had a power outage or surge: try a full power cycle by turning the unit off at the remote, then switching off the circuit breaker for 5 minutes and restoring. If A1 persists, the board may need replacement.

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A3 — Drain float switch activated (the most serviceable A-code)

The condensate float switch inside the indoor unit detected water at flood-prevention level. The unit shut down to prevent water damage.

This is usually a clogged drain and is DIY-appropriate.

1. Locate the indoor unit’s condensate drain. It’s a small pipe or tube exiting the back or bottom of the indoor unit.
2. Check for visible blockage at the drain outlet (where the tube empties into a bucket, condensate pump, or drain pipe).
3. Clear the drain line: for mini-splits, use a wet-dry vac on the drain outlet end, or blow gently with compressed air from the drain outlet (air pushes toward the unit — wear eye protection).
4. If a condensate pump is installed: check that the pump is running and the float inside the pump reservoir isn’t stuck. A small screwdriver can unstick a stuck float.
5. After clearing: reset by cycling power. The unit should run without triggering A3.

If A3 returns after clearing: the float switch itself may be stuck or failed (float is stuck in the triggered position). A tech can bypass the switch temporarily to confirm, then replace it.

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A5 — Freezing or freeze protection activated

The unit detected an over-cooling condition at the indoor coil. This is Daikin’s freeze protection mode.

Most common causes:

1. Dirty filter — check and clean the air filter behind the indoor unit front panel first.
2. Low refrigerant — requires a technician with gauges and EPA 608 certification.
3. Very low outdoor temperature — running the unit in cooling mode below its operating ambient range.

What to do:

1. Turn off cooling mode; switch to fan only to thaw the coil (30–60 minutes).
2. Clean the filter.
3. If A5 returns with a clean filter and normal ambient temperature, refrigerant undercharge is likely — call a tech.

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A6 — Indoor fan motor fault

The indoor unit’s fan motor is running outside its expected speed range, or the controller can’t detect the fan motor’s feedback signal.

Check:

• With unit off and unplugged, gently rotate the indoor blower drum by hand. It should spin freely. Resistance or grinding = motor bearing failure.
• Inspect for debris (insects, accumulated lint) jamming the blower.

Fan motor replacement requires a technician — these are DC variable-speed motors with integrated controllers.

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C4 — Heat exchanger (coil) temperature sensor fault

The temperature sensor measuring the indoor coil has failed or its reading is outside the expected range.

What to check:

• Inspect the sensor wire where it connects to the control board. Loose, corroded, or broken connector is the most common cause.
• On units recently serviced or cleaned: a sensor may have been dislodged from the coil fins. It should clip snugly to the fin surface.

A tech can test sensor resistance against the expected temperature curve and replace a failed sensor (typically an inexpensive thermistor, $10–30 part, plus labor).

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C9 — Remote sensor fault (on units with a remote temperature sensor)

The remote indoor temperature sensor (sometimes used to detect room temperature more accurately than the indoor unit’s built-in sensor) has failed or is disconnected.

Verify the sensor cable is connected at both the unit and the sensor location. If connected and error persists, the sensor needs replacement.

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E1 — Outdoor unit PCB fault

The outdoor unit’s main control board has detected an internal fault. Same situation as A1 — not homeowner-serviceable. Requires a technician.

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E3 — High-pressure protection

The compressor discharge pressure exceeded the upper safety limit. The unit shut down to protect the compressor.

Causes:

• Very high outdoor temperature on the cooling cycle (compressor working against a very hot condenser)
• Dirty or blocked outdoor condenser coil (reduced heat rejection)
• Refrigerant overcharge
• Non-condensables (air) in the refrigerant circuit
• Failed outdoor fan

What to check yourself:

• Is the outdoor unit’s airflow blocked? Clear any debris (leaves, grass clippings) from the condenser fins. Ensure there’s at least 12 inches of clearance around the outdoor unit.
• Is the outdoor fan spinning? Stand near the unit during operation — you should hear and feel airflow from the top.

If the outdoor coil is clear and fan is running: refrigerant system issue requiring a tech.

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E4 — Low-pressure protection

The suction pressure dropped below the lower safety limit. Usually indicates refrigerant undercharge, a leak, or a refrigerant system restriction.

This requires a technician. Low refrigerant requires recovery, leak detection, repair, and recharge — EPA 608 certified, specialized equipment.

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E5 — Overcurrent (compressor motor)

The compressor drew excessive current. Causes: failing compressor, low voltage, refrigerant system fault causing high operating pressures.

Call a technician. Compressor current testing and refrigerant pressure measurements are required.

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E7 — Outdoor fan motor fault

Similar to A6, but for the outdoor unit fan motor. The outdoor fan is running out of range or not detected.

Check: is the outdoor fan blade visually turning when the unit operates? Any debris caught in the blades? If the fan isn’t turning and the compressor is running, the unit will quickly trip on E3 (high pressure).

Fan motor replacement is a technician job.

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E9 — Inverter compressor fault

The inverter drive (variable-frequency controller for the compressor motor) has detected a fault. This is an outdoor unit control board or compressor inverter issue — requires technician diagnosis.

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U0 — Refrigerant shortage protection

The system has detected conditions consistent with low refrigerant charge (low suction superheat, rapid cycling). This is an E4-family fault.

Call a technician. Refrigerant system diagnosis and service required.

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U2 — Main power supply abnormality

The outdoor unit detected power supply voltage outside its acceptable range.

Check:

• Verify the outdoor unit’s circuit breaker is fully seated at the main panel.
• Check that the disconnect switch near the outdoor unit is fully closed.
• If power appears normal but U2 persists, the unit’s power module may be damaged — technician required.

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U4 / UA — Indoor/outdoor communication error

The indoor and outdoor units have lost communication. Same diagnostic as Mitsubishi E6: check the communication wiring.

What to check:

1. Inspect the communication terminals on both the indoor unit (behind the front panel, at the terminal block) and the outdoor unit (at the screw terminal block on the electrical section).
2. Look for loose wires, corroded terminals, or damaged cable along its run.
3. If the communication cable runs through or near a penetration in the wall, check for damage there.
4. If recently serviced: confirm the installer reconnected the communication terminals correctly (the polarity matters on some Daikin systems — reversing the two communication wires causes U4).

U4 that persists after checking connections typically requires control board testing.

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The filter cleaning reminder is not an error code

Daikin mini-splits track operating hours and display a maintenance reminder after a set interval. This appears as a light on the indoor unit panel (often labeled “FILTER”) or a message on the remote. It’s a maintenance prompt, not a fault.

To clear it: clean the washable filter behind the front panel, then press and hold the FILTER RESET button (if present) on the remote or indoor unit for 2–3 seconds. Refer to your remote’s manual for the specific reset procedure.

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When to call a licensed HVAC technician

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FAQ

How do I find my Daikin mini-split model number? Open the front panel of the indoor unit — the nameplate is on the unit chassis, usually visible once the filter is removed. It shows the model number (e.g., FTXS15LVJU), serial number, and electrical specs. Search for your model number plus “service manual PDF” to find the code table.

Does a Daikin mini-split have a reset button? There’s no dedicated reset button on most models. Reset by powering the unit off from the remote, waiting 5 minutes, and powering back on. For a hard reset, switch off the circuit breaker for the system for 5 minutes.

Can I add refrigerant to my Daikin mini-split myself? No — mini-splits use R-410A or R-32 refrigerant, handling of which requires EPA 608 certification. The refrigerant charge must be weighed in precisely — overcharge causes E3 (high pressure); undercharge causes E4 or U0. Adding refrigerant without recovery and weighing can damage the compressor.

My Daikin unit shows an error code not listed here. What should I do? Find your model number and download the service manual from Daikin North America (daikinapplied.com or daikinacdealers.com for residential units). The fault code table covers every code for your unit. Your HVAC contractor can also look up codes through Daikin’s dealer portal.