Daikin Error Codes & Diagnostics
Complete diagnostic directory for official Daikin fault codes. Verify root causes, safe troubleshooting steps, and replacement part numbers before calling a technician.
Daikin A3: drain level control abnormality on the indoor unit
Daikin assigns A3 to the drain level control system in the indoor unit division of its malfunction chart. The control detected that the condensate level or the drain system response was outside normal, and it stopped operation to prevent the tray overflowing. The chart names the system, which is why A3 covers the float switch, the drain pump, and the path between them rather than any one of them. Applies to: Daikin indoor units covered by the SM-TS3 malfunction code chart, spanning room air, SkyAir, and VRV indoor equipment A3 is read from the Daikin After Sales Service malfunction code chart, which divides codes by unit rather than by model. The chart gives the meaning of the letter and detail code; the component layout behind it comes from the service manual for the specific indoor unit. A wall-mounted room air unit without a drain pump does not carry the same detection. Owner-safe checks: Select fan operation or switch the affected indoor unit off so the coil stops condensing while the fault is outstanding. | Record the unit number shown beside A3 and the room that unit serves, which identifies the address for service. | Check whether the external condensate discharge point produced any water during the period the unit had been cooling. Qualified technician: Opening a cassette decoration panel, testing a float switch, or clearing a drain pan inside the indoor unit is qualified service work on this equipment. | Any water that has reached ceiling material, lighting, or an electrical accessory is a stop condition, and the indoor unit should be isolated rather than restarted.
Daikin A5 error code: freeze-up or peak-cut
On Daikin 15 and 19 Series equipment, A5 represents freeze-up protection in cooling or heating peak-cut control when the indoor heat-exchanger temperature crosses the documented limits. Applies to: Daikin 15 and 19 Series The two meanings described here come from the Daikin service manual covering the 15 and 19 Series. Which protection you are looking at depends on the mode the system was running, and other Daikin ranges assign A5 within their own code structure, so start from the manual that matches your model plate. Owner-safe checks: Turn the unit off and inspect the user-removable filter for loading; clean it exactly as the model manual directs. | Confirm furniture, curtains, or closed louvers are not blocking the indoor intake or outlet. Qualified technician: Persistent icing, thermistor testing, coil cleaning beyond routine maintenance, and PCB diagnosis need qualified service. | Do not chip ice from a coil or use heat sources to force thawing.
Daikin A6: indoor fan motor locked, overloaded, or badly connected
Daikin lists A6 in the indoor unit division as a fan motor malfunction, described as the motor being locked, overloaded, or suffering from a faulty connection. All three are ways of saying the board commanded a fan speed and did not get the feedback it expected, so the code is about the command-and-feedback loop rather than about a burnt-out motor. Applies to: Daikin indoor units covered by the SM-TS3 malfunction chart, including room air, SkyAir, and VRV indoor equipment The definition here comes from the Daikin malfunction code chart, which is organised by division and detail code rather than by model. Indoor fan arrangements differ sharply between a wall unit, a cassette, and a ducted unit, so the mechanical cause behind the same code is model-specific and is read from that unit's service manual. Owner-safe checks: Switch the affected indoor unit off and leave it off, since running the outdoor unit against a stalled indoor coil is what the protection prevents. | Confirm the filters, front panel, and any decoration panel are correctly seated and latched after recent cleaning. | Write down any noise heard before the fault, the fan speed it occurred at, and roughly when it started. Qualified technician: Reaching into the fan housing, freeing a wheel, and testing motor feedback or winding condition require the indoor casing to be opened by a qualified technician. | Do not attempt to turn the fan wheel by hand through a grille or outlet. The blade edges and the drive arrangement are not designed for that access.
Daikin C9: the suction air thermistor the room setting depends on
Daikin places C9 in the sensor division against the suction air thermistor, and describes the fault as an abnormal resistance, which covers a disconnection and a short circuit. That sensor reads the air entering the indoor unit, so it is the value the system treats as room temperature and the basis of every capacity decision it makes. Applies to: Daikin indoor units covered by the SM-TS3 malfunction chart, where the C division covers sensor systems The C division on the Daikin chart groups sensor systems, and the detail code selects which sensor. Where a sensor sits inside a particular indoor unit, and what resistance curve it follows, comes from the service manual for that model. A code alone does not tell a technician which physical part to reach for. Owner-safe checks: Note the unit number shown beside C9 and which room it serves before any power is interrupted. | Compare the temperature the controller displays, if it is still visible, against a separate thermometer near the intake. | Confirm filters and panels are correctly seated, and note whether the fault followed any recent cleaning or service. Qualified technician: Measuring thermistor resistance against the published curve and inspecting the indoor board connectors require the casing to be opened by a qualified technician. | A code accompanied by a burning smell, discoloration, or a protective device operating is a stop condition rather than a sensor question.
Daikin E7: the outdoor fan motor system stopped reporting what it should
Daikin places E7 in the outdoor unit division as a malfunction of the outdoor fan motor system. The word system is doing real work in that phrase: the entry covers the motor, the drive circuit that powers it, and the feedback path that confirms it turned. Seeing the fan stationary confirms the symptom but not the cause. Applies to: Daikin outdoor units covered by the SM-TS3 malfunction chart, including room air, SkyAir, and VRV outdoor equipment This meaning is taken from the Daikin malfunction code chart, which assigns codes by division rather than by model. Outdoor fan arrangements differ between a single-fan room air unit and a twin-fan SkyAir or VRV frame, and the checks for each come from the service manual covering that outdoor model. Owner-safe checks: Stop the system from the controller so it is not making repeated start attempts against a fan that is not turning. | Look at the outdoor unit from a safe distance and note whether the blade is completely static, turning slowly, or turning normally. | Isolate the outdoor unit at its dedicated switch before removing leaves or debris resting against the outside of the guard. Qualified technician: Testing the fan drive output, measuring motor windings, and inspecting feedback wiring inside an outdoor enclosure are energised tasks for a qualified technician. | Never reach through or remove the fan guard. A variable-speed outdoor fan can start without notice, including while the system appears to be idle.
Daikin F3: discharge pipe temperature outside what the circuit allows
Daikin's malfunction chart lists F3 against discharge pipe temperature. The thermistor on the compressor discharge line has reported a temperature the control will not run at, and because refrigerant flow is what keeps that line cool, the reading is a statement about the circuit rather than about the pipe. Applies to: Daikin outdoor equipment covered by the SM-TS3 malfunction chart, spanning room air, SkyAir, and VRV outdoor units Taken from the Daikin After Sales Service malfunction chart, where the F division belongs to the outdoor unit and the detail code selects the subsystem. Sensor positions and the thresholds behind them come from the service manual for the specific outdoor model, so a code alone does not give you a temperature to compare against. Owner-safe checks: Stop calling for heating or cooling and leave the system off, since each further cycle runs the compressor toward the same limit. | Walk the visible line set and outdoor unit looking for oil film or localised frost, and photograph anything unusual without touching it. | Record how long the outdoor unit runs before it stops, and how performance had changed over the preceding weeks. Qualified technician: Charge measurement, leak detection, recovery, and discharge thermistor testing are certified refrigerant activities under EPA Section 608 and under F-Gas rules in the United Kingdom and European Union. | Adding refrigerant without finding the loss, or restarting to see whether the code stays away, both put the compressor back into the condition the protection stopped.
Daikin U0 error code: refrigerant shortage on a mini-split
Daikin assigns U0 to a refrigerant shortage. The control has seen the circuit behaving as though there is too little refrigerant, from readings such as a low suction temperature or an abnormal discharge condition. A closed service valve, an undercharge left after install, or a leak all present as U0. Applies to: Daikin room air conditioner splits and multi-split systems that publish U0 in the malfunction code table This meaning follows the Daikin malfunction code table for room air conditioner and multi-split systems that list U0. SkyAir, VRV, and Altherma ranges use their own code sets, so confirm the indoor and outdoor model numbers before applying this page. Owner-safe checks: Note whether the system is newly installed or has a long service history, and whether output faded gradually or stopped suddenly before U0. | Check from the ground for oily residue at pipe joints or unusual frosting on the outdoor unit, without touching the pipework or valves. Qualified technician: Refrigerant-circuit diagnosis and charging require a qualified technician with the applicable refrigerant handling credential.
Daikin U2: power supply malfunction or an instantaneous power failure
In the Daikin malfunction chart, U2 belongs to the system division and reads as a malfunction of the power supply or an instantaneous power failure. That covers both a supply that briefly disappeared and a supply that is present but outside what the drive will work with, which is why one U2 after a storm and a U2 that repeats every day mean unrelated things. Applies to: Daikin equipment covered by the SM-TS3 malfunction chart, where the U division reports system-level conditions across room air, SkyAir, and VRV The reading is taken from the Daikin After Sales Service chart, where the U division covers system conditions rather than one unit. Some Daikin equipment, including the room air lines, presents a related shortage entry as U0, so confirm which digit is displayed before treating the fault as electrical. Owner-safe checks: Check whether a power cut, a storm, or electrical work coincided with the code, and write down what you find. | Confirm that the dedicated isolator and any protective device serving the equipment are in their normal operating position. | Read the supply voltage and frequency printed on the outdoor unit data plate so the figures are available to service. Qualified technician: Measuring supply voltage under load, inspecting isolator and terminal connections, and testing the drive input are qualified electrical tasks. | A protective device that operates repeatedly, a burning smell, or heat at an isolator is a stop condition. Leave the supply off and arrange an electrical inspection.
Daikin AC Error Code U4: Transmission Failure Between Indoor & Outdoor Units
Communication Error (Loss of data transmission between the indoor unit PCB and the outdoor condenser unit PCB).
Daikin U4 error code: indoor-outdoor transmission error
For the documented Daikin SkyAir RZR-P and RZQ-P(9) systems, U4 is a transmission error between indoor and outdoor units after normal communication is absent for the specified interval. Applies to: SkyAir RZR-P and RZQ-P(9) This definition is taken from the SkyAir service manual covering RZR-P and RZQ-P(9) equipment and the indoor units listed with it. Daikin uses structured code letters across product lines that share little else, so a U4 on VRV, Altherma, or a residential split needs the manual for that line rather than this page. Owner-safe checks: Write down the full controller code and every connected indoor and outdoor model number. | Check only normal user-accessible power controls and note whether other units on the same system operate. Qualified technician: Transmission wiring, fuses, fan motors, and PCBs require qualified electrical diagnosis. | Multi-unit SkyAir systems should be diagnosed as a network rather than by replacing the first board named.
Daikin UA error code: indoor and outdoor unit combination fault
Daikin assigns UA to an improper combination of indoor and outdoor units. The paired models are not compatible, the number of connected indoor units is outside the outdoor unit's limit, the refrigerant types do not match, or a replacement control board was fitted without its combination setting being made. Applies to: Daikin split and multi-split systems that publish UA for an indoor and outdoor combination fault This meaning follows the Daikin malfunction code table for split and multi-split systems that list UA. SkyAir and VRV ranges assign UA-adjacent codes differently, so confirm the outdoor model and every connected indoor model before acting. Owner-safe checks: Note whether UA appeared at first commissioning, after equipment was combined from different kits, or right after a control board was replaced. | Write down the outdoor model and every indoor model with the room it serves, so the installer can check the combination against Daikin's data. Qualified technician: Changing paired equipment, removing indoor units from a multi-split, and making a replacement board's combination setting are all installer or technician tasks.
Daikin UF error code: piping and wiring do not match
Daikin assigns UF to a mismatch between the control wiring and the refrigerant piping. On a multi-split the cable from an indoor head lands on one outdoor port while its pipes connect to a different port, so the system cannot pair a head with its circuit. It also covers wrong field wiring and a shortage detected during the check. Applies to: Daikin multi-split systems and splits that publish UF for a wiring and piping combination fault This meaning follows Daikin literature for multi-split and split systems that list UF as a field wiring and piping combination fault. Other Daikin ranges use different U-series codes, so confirm the outdoor unit and every connected indoor model before acting. Owner-safe checks: Note whether UF appeared at first commissioning or right after an indoor head was added, moved, or rewired, and which zones do not respond. | Keep a list of which room each indoor unit serves so the installer can match heads to outdoor ports quickly. Qualified technician: Tracing cables and pipes to outdoor ports and correcting the connections means opening the outdoor electrical cover and working at the terminals, which is installer work.