Fujitsu Mini-Split Code 74
Soft lockoutShown as: OPERATION lamp blinks 7 times, TIMER lamp blinks 4 times, ECONOMY lamp blinking continuously
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