Fujitsu air conditioner 41 error code: indoor room temperature sensor fault
Also shown as E41
- Urgency
- Medium
- Who can fix it
- Technician job
- Time
- About 15 min
- Repair cost
- $150–$400
What the 41 code means
Error 41 on a Fujitsu mini-split means the indoor room temperature thermistor has detected an abnormal temperature, usually because the sensor is open or shorted. The lamp pattern is 4 operation blinks and 1 timer blink, with the economy lamp flashing.
The room thermistor sits near the air intake. Its resistance changes with temperature, and the indoor board uses it to decide when to run the compressor and how fast. When the reading is impossible, the board shows error 41 and stops.
Fujitsu's diagnosis is to check the thermistor for an open or short, measure its resistance and, if the sensor is fine, replace the controller board.
Common causes
Listed from most to least common.
- Room temperature thermistor failed (open or short circuit)
- Thermistor plug loose on the indoor controller board
- Sensor wire damaged
- Indoor controller board fault
How to fix the 41 code
Unplug the air conditioner or switch it off at the breaker before removing any panel or filter.
Step 1: Reset the power
Switch off the breaker for 5 minutes and turn it back on. A glitch may clear.
Step 2: Check nothing is heating the intake
Make sure no lamp, TV, heater or sunlit window is right under the indoor unit, and that the intake grille is clear.
Step 3: Note how soon it returns
Write down whether 41 appears at start-up or after a while. It helps a technician tell a loose plug from a failed sensor.
Step 4: Book a repair if it repeats
If 41 comes back, stop using the unit and call for service. The sensor is inside the indoor unit.
How to reset the Fujitsu air conditioner
- Turn the system off with the remote or wired controller.
- Switch off the breaker for the system, and the outdoor disconnect switch if there is one. Leave the power off for at least 5 minutes.
- Restore power and turn the unit back on. The compressor normally waits a few minutes before starting, so give it time before judging.
- If the same code or blink pattern comes back, the fault is still there. Work through the fix steps above, or call a Fujitsu contractor or other licensed HVAC technician.
When to call a technician
A technician needs to check the thermistor for an open or short, measure its resistance against Fujitsu's chart and check the controller board. The sensor is a cheap part, so most of the cost is labor.
A typical repair for this code costs $150–$400 in the US, including parts and labor. Prices vary by area and model.
Models this applies to
- Halcyon wall-mounted mini-splits (ASU indoor, AOU outdoor)
- Halcyon floor, ceiling cassette and slim duct units (AGU, AUU, ARU)
- Halcyon multi-zone systems (RLF series)
- Ducted and ceiling-suspended units (RGLX, RULX series)
Codes can differ slightly between models. Your owner's manual is the final word and is available from Fujitsu support.
Frequently asked questions
›How many blinks is error 41?
The operation lamp blinks 4 times and the timer lamp blinks once, while the economy lamp flashes continuously.
›Is error 41 expensive to fix?
Usually not. A thermistor costs little. Expect roughly $150 to $400 including the service call. A failed controller board costs more.
›What is the difference between 41 and 42?
41 is the room air sensor. 42 is the sensor on the indoor coil pipe. Both are indoor sensor faults with the same basic fix.