Fujitsu Mini-Split: 7 Flashes
A Fujitsu mini-split LED pattern starting with 7 flashes matches 7 documented codes: 71, 72, 73, 74, 75, 76, 77. Watch the full pattern (short vs. long flashes) to tell them apart — all 7 are explained below.
Code 71: Discharge thermistor error
Discharge thermistor error. The sensor on the compressor discharge pipe read as open or shorted, either at power up or while the compressor was running.
Manual wording: “Discharge Thermistor Error - When discharge pipe temperature thermistor open or short-circuit is detected at power on or while running the compressor.”
Documented for: RGLX, RL2/RLS3/RLB/RLXB, RLF/RLF1 outdoor units
Likely causes, most common first
- Loose, removed, or wrongly landed thermistor connector
- Open or shorted discharge thermistor
- Failed outdoor main PCB
What you can safely check yourself
- Turn the power off at the outdoor disconnect and breaker for about 5 minutes, then restore power
When to call a technician
The discharge thermistor sits on hot refrigerant piping inside the condenser cabinet. Replacing it is a technician's job.
A Fujitsu mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- 410A Mini-Split Troubleshooting Guide (Part # 6-26-FG2020 Rev. 5/2019) (Fujitsu General America, Inc., All R410A Halcyon mini-splits: RGLX, RL2/RLS3/RLS3H/RLS3Y/RLB/RLXB/RLXEH wall mounted, RLF/RLF1 multi-zone indoor units, RLXFZ multi-zone outdoor units, RML/RMLQ, RULX/RSLX universal-mount, RCLX cassettes) · checked 2026-08-25
Code 72: Compressor thermistor error
Compressor thermistor error. The compressor body temperature sensor is open or short-circuited.
Manual wording: “Compressor Thermistor Error - Compressor temperature thermistor is open or short-circuited while power is on or running the compressor.”
Documented for: RGLX, RL2/RLS3/RLB/RLXB, RLF/RLF1 outdoor units
Likely causes, most common first
- Erroneous connection or removed connector at the compressor thermistor
- Thermistor resistance out of specification
- Failed outdoor main PCB
What you can safely check yourself
- Turn the power off at the outdoor disconnect and breaker for about 5 minutes, then restore power
When to call a technician
The sensor mounts on the compressor shell inside the condenser. Only a technician should replace it.
A Fujitsu mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- 410A Mini-Split Troubleshooting Guide (Part # 6-26-FG2020 Rev. 5/2019) (Fujitsu General America, Inc., All R410A Halcyon mini-splits: RGLX, RL2/RLS3/RLS3H/RLS3Y/RLB/RLXB/RLXEH wall mounted, RLF/RLF1 multi-zone indoor units, RLXFZ multi-zone outdoor units, RML/RMLQ, RULX/RSLX universal-mount, RCLX cassettes) · checked 2026-08-25
Code 73: Heat exchanger
Heat exchanger (pipe) thermistor error at the outdoor unit. The outdoor coil pipe sensor is open or short-circuited.
Manual wording: “Heat Exchanger (Pipe) Thermistor Error - When heat exchanger temperature thermistor open or short-circuit is detected at power up or while running the compressor.”
Documented for: RGLX, RL2/RLS3/RLB/RLXB, RLF/RLF1 outdoor units. On 30RLXEH this position also covers heat exchanger middle temperature and heat exchanger liquid temperature thermistor errors
Likely causes, most common first
- Loose or erroneous connector connection
- Open or shorted outdoor pipe thermistor
- Failed outdoor main PCB
What you can safely check yourself
- Turn the power off at the outdoor disconnect and breaker for about 5 minutes, then restore power
When to call a technician
Replacing the outdoor coil sensor means working inside the condenser cabinet. Call a technician.
A Fujitsu mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- 410A Mini-Split Troubleshooting Guide (Part # 6-26-FG2020 Rev. 5/2019) (Fujitsu General America, Inc., All R410A Halcyon mini-splits: RGLX, RL2/RLS3/RLS3H/RLS3Y/RLB/RLXB/RLXEH wall mounted, RLF/RLF1 multi-zone indoor units, RLXFZ multi-zone outdoor units, RML/RMLQ, RULX/RSLX universal-mount, RCLX cassettes) · checked 2026-08-25
Code 74: Outdoor thermistor error
Outdoor thermistor error. The outdoor ambient air temperature sensor is open or short-circuited.
Manual wording: “Outdoor Thermistor Error - When outdoor temperature thermistor is open or a short-circuit is detected at power on or while running the compressor.”
Documented for: RGLX, RL2/RLS3/RLB/RLXB, RLF/RLF1 outdoor units
Likely causes, most common first
- Loose or erroneous connector connection
- Open or shorted outdoor air thermistor
- Failed outdoor main PCB
What you can safely check yourself
- Turn the power off at the outdoor disconnect and breaker for about 5 minutes, then restore power
When to call a technician
The outdoor air sensor and its plug are inside the condenser cabinet. Have a technician check and replace it.
A Fujitsu mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- 410A Mini-Split Troubleshooting Guide (Part # 6-26-FG2020 Rev. 5/2019) (Fujitsu General America, Inc., All R410A Halcyon mini-splits: RGLX, RL2/RLS3/RLS3H/RLS3Y/RLB/RLXB/RLXEH wall mounted, RLF/RLF1 multi-zone indoor units, RLXFZ multi-zone outdoor units, RML/RMLQ, RULX/RSLX universal-mount, RCLX cassettes) · checked 2026-08-25
Code 75: Suction gas thermistor error
Suction gas thermistor error. The suction gas temperature sensor has shorted or gone open.
Manual wording: “Suction Gas Thermistor Error - Suction gas temperature thermistor has shorted or open detected.”
Documented for: RLF/RLF1 multi-zone systems on RLXFZ outdoor units
Likely causes, most common first
- Loose or erroneous molex plug connection
- Thermistor resistance out of specification
- Failed outdoor main PCB
What you can safely check yourself
- Turn the power off at the outdoor disconnect and breaker for about 5 minutes, then restore power
When to call a technician
The suction gas sensor is on refrigerant piping in the condenser. A technician must check and replace it.
A Fujitsu mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- 410A Mini-Split Troubleshooting Guide (Part # 6-26-FG2020 Rev. 5/2019) (Fujitsu General America, Inc., All R410A Halcyon mini-splits: RGLX, RL2/RLS3/RLS3H/RLS3Y/RLB/RLXB/RLXEH wall mounted, RLF/RLF1 multi-zone indoor units, RLXFZ multi-zone outdoor units, RML/RMLQ, RULX/RSLX universal-mount, RCLX cassettes) · checked 2026-08-25
Code 76: 2-way or 3-way valve thermistor error
2-way or 3-way valve thermistor error. The temperature sensor on a service valve is open or short-circuited while power is on or the compressor is running.
Manual wording: “2-Way Valve Thermistor Error - When 2-way valve temperature thermistor is open or short-circuited while power is on or while running the compressor.”
Documented for: RLF/RLF1, LPAS and LUAS1 multi-zone indoor units; AOU18/24/36RLXFZ and AOU24/36RML outdoor units
Likely causes, most common first
- Erroneous connection or removed connector at the valve thermistor
- Thermistor resistance out of specification
- Failed outdoor main PCB
What you can safely check yourself
- Turn the power off at the outdoor disconnect and breaker for about 5 minutes, then restore power
When to call a technician
These sensors sit on the service valves inside the condenser or branch box and are ohm-checked against Fujitsu's resistance chart. That is technician work.
A Fujitsu mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- 410A Mini-Split Troubleshooting Guide (Part # 6-26-FG2020 Rev. 5/2019) (Fujitsu General America, Inc., All R410A Halcyon mini-splits: RGLX, RL2/RLS3/RLS3H/RLS3Y/RLB/RLXB/RLXEH wall mounted, RLF/RLF1 multi-zone indoor units, RLXFZ multi-zone outdoor units, RML/RMLQ, RULX/RSLX universal-mount, RCLX cassettes) · checked 2026-08-25
- 2-Way / 3-Way Valve Thermistor Error - Fujitsu General Help Center (Fujitsu General America, Inc., RLF/RLF1 multi-zone indoor units, LPAS and LUAS1 multi-zone indoor units, RLXFZ / RML multi-zone outdoor units) · checked 2026-08-25
Code 77: Heat sink thermistor error
Heat sink thermistor error. The heat sink temperature sensor built into the power module is open or shorted.
Manual wording: “Heat Sink Thermistor Error - Heat sink temperature thermistor (built-in IPM) is open or shorted.”
Documented for: RGLX, RL2/RLS3/RLB/RLXB, RLF/RLF1 outdoor units
Likely causes, most common first
- Failed inverter PCB (the sensor is built into the module on wall-mounted models)
- Erroneous connection or removed connector
- Thermistor resistance out of specification
What you can safely check yourself
- Turn the power off at the outdoor disconnect and breaker for about 5 minutes, then restore power
When to call a technician
On wall-mounted models this sensor is part of the inverter board, so the fix is a board replacement by a licensed technician.
A Fujitsu mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Source
- 410A Mini-Split Troubleshooting Guide (Part # 6-26-FG2020 Rev. 5/2019) (Fujitsu General America, Inc., All R410A Halcyon mini-splits: RGLX, RL2/RLS3/RLS3H/RLS3Y/RLB/RLXB/RLXEH wall mounted, RLF/RLF1 multi-zone indoor units, RLXFZ multi-zone outdoor units, RML/RMLQ, RULX/RSLX universal-mount, RCLX cassettes) · checked 2026-08-25