Fujitsu Mini-Split Error Code 3: How to Fix It
Medium 30-60 minutes Medium Severity
Verified June 2026
- Error Code
- 3
- Brand
- Fujitsu
- Product Type
- mini_split
- Severity
- Medium
- DIY Difficulty
- Medium
- Estimated Fix Time
- 30-60 minutes
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Tools You'll Need
- Multimeter with resistance (ohms) setting
- Voltage tester
- Screwdriver (Phillips)
- Wire connectors or soldering iron
- Replacement thermistor (10k NTC, Fujitsu compatible)
How to Fix Error Code 3
-
Turn Off Power and Safety Prep
Always disconnect power before servicing the unit to avoid electrical shock. -
Locate the Indoor Unit Thermistor
-
Test Thermistor Resistance
-
Replace the Thermistor
Use only a thermistor with the same resistance curve to prevent system damage. -
Reassemble and Test
Parts You May Need
Indoor coil thermistor (10k NTC)
Check Price on Amazon
Indoor coil thermistor (10k NTC)
Check Price on Amazon
Indoor coil thermistor (10k NTC)
Check Price on Amazon
Indoor coil thermistor (10k NTC)
Check Price on Amazon
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When to Call a Professional
Call an HVAC technician if the error persists after replacing the thermistor, or if you are uncomfortable working with electrical components and refrigerant lines. Also, if the control board appears damaged, professional diagnosis is recommended.Frequently Asked Questions
Can I still use my Fujitsu mini-split with error code 3?
No, the unit will typically stop heating or cooling to protect the compressor. Continued operation may cause further damage.
Where is the thermistor located on a Fujitsu mini-split?
Inside the indoor unit, on the evaporator coil (heat exchanger). Remove the front panel and look for a small probe clipped to the copper tubing.
What is the correct resistance for a Fujitsu mini-split thermistor?
The indoor coil thermistor is typically a 10k ohm NTC type. At 77°F (25°C), resistance should be around 10k-15k ohms. Check your model's service manual for exact specs.
Can a dirty filter cause error code 3?
No, error code 3 specifically indicates a thermistor fault, not airflow. However, a dirty filter can cause other coil temperature errors (e.g., error code 9).
Do I need to recover refrigerant to replace the thermistor?
No, removing the thermistor does not open the refrigerant circuit. It is simply clipped onto the coil and can be replaced without any refrigerant work.