Fujitsu Halcyon Air Conditioner Troubleshooting Guide!

It takes the proper understanding of the Fujitsu Halcyon air conditioner troubleshooting to fix the unit DIY when it fails. That means you don’t have to call an HVAC expert whenever your air con isn’t working.

You can troubleshoot a Fujitsu Halcyon air conditioner that won’t work after a power failure or won’t start at all. You can also fix an option that won’t blow any air, cool, heat, drain or dehumidify or an AC with blinking green lights. 

Those are the everyday air conditioner problems that I’ll discuss here. I’ll also help you interpret the various error codes that may pop up on your Halcyon AC and know how to do a quick reset of the air con. 

Remember, the goal is to avoid an HVAC service call where necessary and get to keep your money in your pocket. So, let’s get into it!

Fujitsu Halcyon air conditioner troubleshooting

In a hurry? Below is a quick Fujitsu Halcyon air conditioner troubleshooting guide.

Quick Fujitsu Halcyon Air Conditioner Troubleshooting Guide

Problem Likely CauseRecommendation
1.AC Won’t Work After Power InterruptionThe AC is on Auto Restart, which takes about 3 minutesWait for the unit to complete the Auto Restart
2.AC Won’t Turn OnFaulty remote control, power interruption (tripped breaker, loose cable, or blown fuse), or faulty timerCheck the remote control and power cable, reset the breaker and replace a blown-up fuse. Call an HVAC expert to fix a malfunctioning timer
3.AC Won’t Blow Air At All Or Weak AirflowLow fan speed due to Auto Defrost, Dry Supper Quiet, or Auto Operation ModeImprove the fan’s speed by disabling the Dry, Super Quite, or Auto Mode. Wait for the Automatic Defrost to take effect if it’s on
4.AC Won’t CoolA dirty filter, obstructed intake grille, high thermostat setting, closed windows/doors, brightly-lit window, close-by heat source, overcrowding, or a refrigerant leakClean the air filter and the obstructed intake grille, lower the thermostat setting, and open some windows or doors. Put curtains on brightly lit windows, move the AC from the heat source and avoid overcrowding. Call an HVAC pro in case of a refrigerant leak
5.AC Won’t HeatPower failure, dirty filter, low thermostat setting, inadequate refrigerant, or malfunctioning sensors or circuit breakerCheck for possible power interruption, clean the filter if dirty, and raise the thermostat setting. In case of inadequate refrigerant or a malfunctioning sensor or circuit board, call an expert
6.AC Won’t Drain Mold cloggingCall an expert if you cannot unclog the condensate drain
7.AC Won’t Dehumidify Mold clogging or oversized unitCall an expert to fix mold clogging and downsize the AC if it’s oversize
8.Blinking Green LightsDirty unitClean the AC, more so the intake grille

8 Common Fujitsu Halcyon Problems for Troubleshooting

Below are Fujitsu Halcyon air conditioner troubleshooting guides for eight common Fujitsu AC issues:

1. Fujitsu Halcyon Air Conditioner Not Working Immediately After Power Interruption

Something doesn’t have to be wrong to explain why your Fujitsu air conditioner won’t kick in as soon as there’s a power interruption. Often, the unit goes on an Auto Restart mode where the compressor takes about 3 minutes before running. 

The Auto Restart mode generally protects the AC from potential damage. 


Wait for the AC to Auto Restart. The automatic process takes about 3 minutes. If the AC doesn’t restart, you can call an expert. 

2. Air Conditioner Won’t Start/Turn On

Sometimes the Fujitsu Halcyon won’t power on, and there are three likely causes: a non-responsive remote control, power interruption, or faulty timer. 

Let’s discuss the trio:

a) Non-responsive Remote Control

If the unit doesn’t turn on when you press the remote control, the remote control could be the problem. It could be that the batteries are exhausted or improperly installed.   

It could also be that you are operating the remote at a distance of more than 20 feet or something such as a wall blocking the signal. So, you’ve to consider all those possibilities.  


Consider replacing the remote control’s batteries, especially if it has been a while. And while at it, ensure you install them correctly (don’t interchange their polarity).

Also, move closer to the AC when operating the remote (keep the range under 20 feet).

And more importantly, avoid any walls which could be obstructing the signals. If the remote control still doesn’t work, press the ‘reset button’ on the remote to reset it. 

Fujitsu Halcyon problems

b) Power Interruption 

If there’s a power interruption before starting the air conditioner, it won’t turn on. In that case, consider these three issues:

  • Loose power cord – The AC won’t turn on unless you plug the power cable into the power socket. It’s also important that the AC is firmly plugged in for it to power on. 
  • Flipped breaker – During a power surge, the breaker will likely flip off to protect the AC. So, you ought to check it. 
  • Blown-up fuse – A power surge can also blow up the fuse to protect the AC. Thus, test the fuse for continuity using a multimeter to determine if it’s faulty.


Ensure the dryer’s power cable is plugged in, and it should be firm. Reset the breaker if it’s off and change the fuse if it’s faulty. 

c) Faulty Timer 

A malfunctioning timer is another thing that’ll prevent your Halcyon air conditioner from starting. So, consider this as your last possibility if the issue is not a non-responsive remote or power interruption. 


Talk to a Fujitsu air conditioner expert when the timer is not operating. It requires special skills and tools to replace a bad timer.

3. Fujitsu Halcyon Not Blowing Air at All or Weak Airflow

At times, the Halcyon air conditioner won’t blow any air; if it does, the airflow is weak. Often, it’s because the fan is running at a very slow speed which you cannot quickly notice.

Consider that the unit may be set on any of these slow-speed modes. 

  • Automatic Defrost mode – The Automatic Defrost takes about 7 – 15 minutes, and during that time, the fan spins at a lower speed, almost unnoticeable.
  • Super-Quiet mode – The fan also spins at an almost untouchable low speed.
  • Auto Mode –Auto Mode allows the fan to run languidly.
  • Dry Mode – Check if the unit is in Dry Mode, which slows down the fan’s speed. 


While you cannot do anything about the “Automatic Defrost’ mode, you can disable/deselect the other modes to improve the fan’s speed. As for Automatic Defrost, wait up to 15 minutes for the cycle to complete.

4. Fujitsu Halcyon Air Conditioner Not Cooling

Your Fujitsu Halcyon won’t cool for different reasons. They include:

  • Dirty air filter – Dirt blocks the air filter and stops cold air from leaving the AC to cool your space. So, inspect your air filter for dirt clogging. 
  • Obstructed intake grille – The intake grille can get dusty, and the AC cannot blow cold air once it does. 
  • High thermostat setting – If the thermostat is set at a high temperature, your AC will blow hot air instead of cold air. 
  • Closed windows/doors – If all the windows and doors are closed, especially in the summer, the room will overheat, and the extra heat will prevent the AC from cooling correctly. 
  • Big window letting in bright sunlight – If an oversized window allows too much direct sunlight, it could be the reason your AC won’t blow cold air. 
  • Close-by heat source – Burning stoves, ovens, and other heat sources can disrupt your AC’s cooling effect.
  • Overcrowding – If so many of you are thronging in a small room, the Halcyon AC won’t be able to cool at all.
  • Refrigerant leak – Lastly, if the refrigerant leaks, the remaining portion won’t be enough to absorb heat from your room. So, the AC won’t cool. 
Fujitsu Halcyon blinking green light


Check the air filter and the unit’s intake grille for dirt clogging and clean them. Then check the thermostat setting and lower the temperature if it’s high. 

Open some of the windows/doors to release the warm air and if there’s one big window letting in bright sun, put a curtain on it. Move the AC away from a nearby heat source or vice versa, and avoid thronging together in the room.

 But if the issue is a refrigerant leak, talk to an HVAC pro. 

5. Fujitsu Halcyon Not Blowing Hot Air

Sometimes, the reasons why your Fujitsu Halcyon won’t cool are the same reasons it won’t heat. There are, however, some exceptions.

Here are the most typical reasons your air conditioner won’t blow hot air:

  • Power failure – Your AC won’t get hot if there’s a tripped breaker or a blown-up fuse. You need to ensure that’s not the case.
  • Dirty filter – A dirty filter won’t allow hot air to blow, just like it blocks cold air. 
  • Low thermostat setting – If the thermostat setting indicates a lower temperature, the AC won’t heat but cool.
  • Inadequate refrigerant – A low refrigerant will also fail to absorb the cold air, thus preventing your AC from heating. 
  • Malfunctioning sensor – Once the AC’s heat sensors malfunction, the unit won’t heat. 
  • Malfunctioning circuit board – If none of the above issues is stopping your AC from cooling, it’s likely to be a bad circuit board. 


Check the circuit breaker and thermal fuse from tripping off and blowing up, respectively. You’ll need to reset the former if it’s tripped and replace the latter if it lacks continuity. 

Raise the thermostat’s temperature if it’s low and contact an HVAC pro to handle a low refrigerant level or malfunctioning sensor or control board. 

6. Air Conditioner Won’t Drain (or Leak/ Drips Water)

If your Fujitsu Halcyon air conditioner won’t drain or happens to be leaking or dripping water, it’s most likely because of mold clogging in the condensate line. The mold could be blocking the line and causing overflow or poor drainage. 


Call an expert immediately once your AC doesn’t drain, but if you can unclog the drain line, do it. 

7. Air Conditioner Won’t Dehumidify

Your Fujitsu AC won’t remove humid air because of a mold-clogged condensate line. If that’s not it, then it could be that the AC is oversized, thus ineffective for your small space.


Call an expert to inspect the condensate drain for mold clogging and if that’s not it, get a smaller air con unit. 

Fujitsu Halcyon air conditioner not cooling

8. Fujitsu Halcyon Blinking Green Light

Usually, the Fujitsu Halcyon air conditioner flashes the Air Clean lamp green to indicate that the AC system needs cleaning. It begins as a slow flash lasting about 7 seconds, then quick flashes last 3 seconds.


Consider inspecting your air conditioner for dirt clogging, notably its intake grille, and cleaning it. 

Fujitsu Halcyon Air Conditioner Error Codes

While the Fujitsu air conditioner can present different codes to signal a malfunction, the commonest are in the table below:

Fujitsu Halcyon troubleshooting codesInterpretationRecommended Fix 
E:0Remote control communication faultCheck the remote control for fault
E:01Indoor/outdoor communication faultCheck the unit’s interconnecting wires
E:02Missing room sensorReplace the missing room sensor
E:03Short-circuited sensorRepair or replace the sensor
E:08Power supply faultLook for faulty wiring or power failure
E:11Incompatible PCBReplace the PCB as its faulty
E:12Fan failure Check the fan and motor for fault
E:14Failed outdoor PCBReplace the outdoor PCB

How Do You Reset a Fujitsu Halcyon?

Fujitsu air conditioners have a reset button on their remote control, mostly labeled ACL or Reset, that you can press to reset the Fujitsu Halcyon. You need a ballpoint or pin to press the reset button as it’s too small.

Closing Remarks 

Above are essential Fujitsu Halcyon air conditioner troubleshooting guides you can use to get your air conditioner back working again. As shared, you can troubleshoot most of the issues DIY, which means you don’t have to be in a hurry to call an HVAC pro. So, consider the tips to save yourself time and possibly money. 

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