It is important to know how to decode these error codes so that the possible problems with Fujitsu mini split can be diagnosed and the normal operation can be restored in a short period of time.
Error codes are usually a combination of flashing LEDs, alphanumeric codes (e.g. A1, 11, 99, etc.), or blinking patterns on a remote controller in most cases. These codes usually refer you to the typical problems, such as basic electrical problems or more complicated communication, temperature sensor, or motor errors. The information presented in this article is based on the Fujitsu 2019 Troubleshooting Guide but the official installation and service manuals should always be used as a source of model specific information and safety instructions. Remember that not all systems will be exactly the same in the way codes are shown, or they may have extra codes particular to multi-zone or ducted systems.
Note: It is important to note that before you carry out any troubleshooting procedures, it is important to shut off power to your mini split system and wait a few minutes to be on the safe side. In case you have no idea how to service HVAC, call a professional technician to prevent possible damage to the system and even personal injury.
The table below shows most of the common Fujitsu mini split error codes. Every entry will contain:
- Error Code: The alphanumerical or numeric code.
- Description: A short explanation of what the code means.
- Possible Causes: Common underlying problems that cause the code.
- Recommended Solutions: Actions or tests that can assist in solving the problem. There are some solutions that can overlap or need a trained technician in case of large electrical or mechanical work.
| Error Code | Description | Likely Causes | Recommended Solutions |
|---|---|---|---|
| 11 | Serial Communication Error (often at startup) | – Indoor and outdoor units not communicating properly – Wiring errors or loose connections – Incorrect voltage supply | Ensure that the wiring of indoor and outdoor units is proper and well connected . – Do not use wire nuts/splices; wherever possible use continuous wires. – Verify voltages at main panel, condenser and evaporator. – Power reset and system monitor. |
| 12 | Wired Remote Controller Communication Error | – Indoor unit not receiving signals from a wired remote for >1 minute – Disconnected or damaged remote cable | Make sure that the remote cables are solid and intact. Check to see whether there is any damage on the cables; replace them where necessary. Make sure that you are using the right wiring of the remote to your particular model. |
| 15 | Automatic Airflow Adjustment Error | – Fan motor locked, obstructed, or defective – Ambient temperature around the indoor fan motor is abnormally high | Turn off the unit and use your hands to determine whether the fan rotates freely. Clear all the obstacles such as debris. – Check the indoor fan motor (ohms, voltage checks). |
| 18 | External Communication Error | – Loose or disconnected link between the main controller PCB and an external I/O PCB – Miswiring or open cable in accessory connections | See the installation manual of the system to get the correct wiring diagrams. Verify all connectors to the external I/O PCB. Re-seat or replace connectors which are loose. |
| 23 | Combination Error | – The outdoor unit detects an incompatible or incorrect indoor unit type – Wiring for multi-zone or single-zone setup is incorrect | – Make sure the model numbers indoor and outdoor are compatible. – Verify wiring of the installation; rectify miswiring. In case of mismatch, then you might have to change the main PCB on the outdoor unit. |
| 32 | Indoor Unit PCB Model Information Error (EEPROM Error) | – Failure to access or read the indoor unit’s memory – Possible harmonic interference or poor grounding | – Ensure that there is good ground connection on indoor unit. Seek electrical noise sources (e.g. neon lights). In case the issue is still there, the controller PCB might require replacement. |
| 33 | Indoor Fan Motor Electricity Consumption Detection Error | – The voltage or current to the motor is out of allowable limits – A locked or stalled indoor fan motor | Shut down the system and turn the fan manually to determine whether it is stuck. – In case of obstruction of the fan, clear the obstruction and test once again. – Verify surrounding conditions which may lead to overheating. |
| 35 | Manual Auto Switch Error | The system detects the Manual Auto Switch is held down for 60 seconds or more | – Make sure that there are no large appliances on the same circuit which result in large voltage drops. Check the power supply and look out for any faulty contacts. – Make sure that all connectors on the indoor unit are seated. |
| 39 | Indoor Fan Motor Power Supply Error | – External voltage drop or noise affecting the indoor unit supply – Loose or incorrect connections in the power circuit | Check the manual/auto switch of the indoor unit. With the multimeter, check whether the switch is stuck in the pressed position. Change or fix the switch in case it is faulty. |
| 3A | Indoor Unit Communication Circuit Error | – The indoor unit cannot detect proper remote controller signals or lacks a primary remote – Voltage for remote controller circuit is missing | – Check the connection between remote and indoor unit. Check that the remote connector of the indoor unit has ~12 V DC. Change the remote controller when it is not getting power. In case the remote is okay, it is possible that the indoor PCB should be replaced. |
| 41 | Indoor Room Thermistor Error | – The room temperature thermistor is reading abnormally (open or short) | -Check the thermistor to see whether it is damaged. – Measure its resistance to ensure that it is equal to the expected value (see the thermistor chart in manual). In case of all the above, the PCB that controls it might be faulty. |
| 42 | Indoor Heat Exchanger (Pipe) Thermistor Error | – The evaporator pipe thermistor is open, shorted, or has abnormal resistance | Check wiring and connector to see whether it is loose or corroded. – Measure the resistance of thermistor and compare with the correct temperature/resistance chart. – Replace when readings are out of specification. |
| 51 | Indoor Fan Motor Error | – The fan’s rotational speed is less than one-third of its target frequency for over 56 seconds – Overheating or physical blockage | – Switch off power and turn the fan blade to ensure that there is no obstruction. -Check fan motor windings with meter to ensure proper resistance. – Check that the motor is being fed with power. |
| 53 | Drain Pump Error | – Float switch remains activated for more than three minutes – Blocked or clogged drain line | – Verify the float switch moves freely and is not stuck. – Inspect the drain pan and lines for blockage, mold, or debris. – Check that the switch wires and connectors (CN9) are intact. |
| 62 | Outdoor Unit Main PCB Error | – The system’s main outdoor circuit board failed to access its EEPROM – Possible grounding or power supply instability | – Power down the unit, wait several minutes, and restore power. – Check for poor ground connections or sudden voltage drops. – If error recurs, the PCB likely needs replacement. |
| 63 | Inverter Error | – Error signal received from the inverter PCB – Loose or damaged connectors to the inverter board | – Switch off power and check all molex plugs on the inverter board. – Reseat any loose connections. – Replace inverter PCB if the fault persists. |
| 64 | Active Filter / PFC Circuit Error | – Inverter input DC voltage is excessively high (>425 V) or extremely low (<80 V) – Momentary power dips or surges | – Inspect for consistent voltage supply and stable grounding. – Reseat or replace loose connectors to the active filter module. – Refer to module resistance checks (ACTPM). |
| 65 | IPM Error (IPM Module Trip) | – Abnormal current detected in the Intelligent Power Module – Outdoor fan or heat exchanger is blocked, causing overheating | – Clear any debris from the outdoor fan or coil. – Check compressor windings with a multimeter. – Inspect IPM connections on the inverter PCB. |
| 71 | Discharge Thermistor Error | – The compressor’s discharge temperature sensor is open or shorted | – Inspect the connector for looseness. – Measure thermistor resistance and compare to spec. – Replace the sensor if out of range. |
| 72 | Compressor Thermistor Error | – The sensor for measuring compressor temperature is open or shorted | – Confirm the connector is firmly seated. – Check thermistor resistance. – Replace thermistor or check associated PCB if the reading is not within range. |
| 73 | Heat Exchanger (Pipe) Thermistor Error | – The outdoor heat exchanger sensor has an open or short circuit | – Look for corroded or loose connector. – Compare thermistor readings with valid temperature/resistance tables. – If the sensor is functional, the main PCB may be at fault. |
| 74 | Outdoor Thermistor Error | – The outdoor ambient temperature sensor is open or shorted | – Inspect connector at the outdoor unit. – Verify thermistor ohms against expected values. – Replace sensor if defective. |
| 84 | Current Sensor Error | – The outdoor inverter detects 0 A even though the compressor is running above ~56 rps – Loose or disconnected current sensor wire | – Switch off the system. – Check the current sensor connection for damage or looseness. – Reseat connections or replace the sensor if found faulty. |
| 86 | High Pressure Switch Error | – The high-pressure switch is detected as open for >10 seconds – System might be overcharged or experiencing blocked airflow | – Temporarily cut power (3–5 minutes), then restore it. – Verify the high-pressure switch is closed when the system is off. – If switch is open or ohms are out of range, replace the switch. |
| 94 | Overcurrent Error | – Overcurrent event detected repeatedly after compressor starts – Possibly caused by a clogged heat exchanger or a failed outdoor fan | – Clean outdoor coil of debris. – Inspect the outdoor fan motor for smooth operation. – Investigate potential wiring issues that cause repeated overcurrent. |
| 95 | Compressor Motor Control Error | – The rotor’s actual position is out of phase (>90°) compared to the detected location – Loose wire harness to compressor or damaged compressor | – Check all compressor wiring. – Measure winding resistance to confirm it meets specification . – Replace compressor or associated PCB if repeated faults occur. |
| 97 | Outdoor Fan Motor Error | – Outdoor fan speed fails to exceed 100 RPM within 20 seconds of starting – Motor locked or overheated | – Turn power off. Attempt to spin the outdoor fan; remove any debris. – Test motor windings and confirm DC voltage supply to motor. – Replace the fan motor if it fails winding or voltage checks. |
| 98 | Outdoor Fan Motor 2 Error (For systems with two outdoor fans) | – Second outdoor fan does not reach 100 RPM or is locked – Overheating or mechanical blockage | – Overheating or mechanical blockage – Same checks as for Error 97: rotate fan by hand, confirm no obstructions. – Check winding resistance and DC voltage to the second fan motor. |
| 99 | 4-Way Valve Error | – Indoor heat exchanger temperature comparison indicates the valve might be stuck or reversed – May not switch properly from heat to cool mode | – 4-way valve solenoid coil and wiring. – Make sure that the valve tubing is clear. – Check that all thermistors (room vs. coil) are reading correctly. |
| A1 | Discharge Temperature Error | – The discharge temperature of the compressor exceeds ~230°F (110°C) – Possible closed or partially closed service valve | Make sure that service valves (liquid or gas side) are wide open. – Inspect the electronic expansion valve (EEV) and strainer. Check to see that there is sufficient refrigerant charge and that there is normal airflow through condenser. |
| A3 | Compressor Temperature Error | – The compressor temperature thermistor measures >226°F (107.8°C) repeatedly within 24 hours – Could be due to restricted refrigerant flow or low charge | -Open 3-way valve, in case it is closed. – Check EEV to see whether there is a blockage. Check the outdoor coil and fan to see whether there is a problem with airflow. – Ensure that the compressor thermistor is well attached and is reading correctly. |
| A5 | Low Pressure Error | – Suction pressure drops below ~7.35 PSI for at least 5 minutes – Repeated 5 times within 2 hours triggers a permanent stop | Make sure that the gas side valve is wide open. – Check that the strainer is not clogged, and look at EEV coil to see that it has the right ohms. – Confirm refrigerant charge, and look at leaks. |
Conclusion
Knowledge of Fujitsu mini split error codes and how to fix them can significantly cut down on downtimes and make your mini split system work optimally.
With the help of the table above and simple checks (checking the connections of the wires, measuring the resistances of thermistors, or cleaning the fans of the obstacles) you can solve simple problems without a long service call.
But there are faults that are more serious and need special HVAC expertise or test equipment. As an example, errors that are complex in nature such as the IPM (intelligent power module), active filter circuitry, or repeated overcurrent trips are often diagnosed professionally.
In case you have to reset errors over and over again or you do not have the required diagnostic tools, do not be afraid to call a certified technician. They will be well trained and equipped with special instruments to identify the malfunctions in the system, including refrigerant gauges, digital multimeters capable of DC measurements, and manufacturer-specific diagnostic software. Moreover, safety must be put first at all times by switching off the power before taking off any panels or wires and also do not forget to adhere to local electrical codes whenever making adjustments or replacements.
Remaining knowledgeable about the meaning of each code and how it can be resolved, you will save your investment in a Fujitsu mini split system and extend its service life and keep the comfort of your indoor environment at a high level during many years.
Keep in mind, early diagnosis and intervention is the key to avoiding more severe (and more costly) breakdowns in the future. In case of doubt, refer to the official manuals of Fujitsu and ask a professional to help you out, your system (and your peace of mind) will be grateful.
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