Fujitsu Mini Split Error Code A3: Compressor Temperature Error (Meaning, Causes, Fixes)
What the code means
Fujitsu's service manuals list E:A3 as "Compressor temperature error (Outdoor unit)". The outdoor unit main PCB, reading the compressor temperature thermistor, makes a protection stop when the compressor temperature reaches 226 °F (108 °C) or more during operation, and the code is set when that happens 2 times within 24 hours. On units without a wired remote, the indoor unit shows it as 10 Operation light flashes and 3 Timer light flashes, with the Economy light flashing continuously; a wired remote shows A3. Fujitsu's forecast of causes is a 3-way valve not opened, a defective electronic expansion valve (EEV) or clogged strainer, an outdoor unit operation failure or foreign matter on the heat exchanger, a compressor temperature thermistor failure, insufficient refrigerant, or a main PCB failure. A3 is different from E:72, which is the compressor thermistor itself reading open or shorted.
Likely causes
- A 3-way service valve that was never fully opened, often after a new install or a repair.
- A defective electronic expansion valve (EEV) or a clogged strainer restricting refrigerant flow.
- Poor heat rejection at the outdoor unit: a blocked or dirty coil, debris or foreign matter on the heat exchanger, or a fan that won't spin freely or a failed fan motor.
- A faulty compressor temperature thermistor reading out of spec.
- Low refrigerant charge from a leak.
- A failed outdoor unit main PCB, which Fujitsu only suspects after the other checks pass.
Safe DIY checks
Turn off power at the breaker and outdoor disconnect before touching the outdoor unit; inverter boards can hold a charge after power is off. Refrigerant work, valve service and thermistor or board replacement should be done by a licensed, EPA-certified HVAC technician.
- Note the light pattern: 10 Operation flashes, 3 Timer flashes and a continuously flashing Economy light means E:A3.
- Turn the system off at the breaker or outdoor disconnect, then look over the outdoor unit. Clear leaves, snow, grass clippings, covers or anything else blocking airflow around the coil and fan.
- With power still off, check that the outdoor fan blade turns freely by hand and nothing is jammed in it, as Fujitsu's check points do.
- Gently clean a dirty outdoor coil with a gentle garden-hose rinse or a no-rinse coil cleaner, and let it dry before restoring power.
- If the system was just installed or serviced, ask the installer to confirm both service valves were fully opened.
- If the code comes back, call a licensed HVAC technician. The valve, EEV, thermistor and refrigerant checks need gauges, tools and EPA certification.
🛠 When to call a pro
- Check that the 3-way valve is open: the gas side for cooling, the liquid side for heating, per Fujitsu. Open it and retest if it's closed.
- Check that the EEV opens and that the strainer isn't clogged.
- Check the outdoor fan, fan motor and heat exchanger for foreign matter and correct operation.
- Disconnect the compressor temperature thermistor from the PCB and compare its resistance to Fujitsu's thermistor resistance chart for that model; replace it if it's out of range.
- Check the refrigerant amount and look for leaks; repair, evacuate and weigh in the correct charge.
- If checks 1 to 5 don't fix it, Fujitsu's last step is to replace the outdoor unit main PCB. For a new or warranty system, contact the installer or Fujitsu General America technical support (866-952-8324) first.
Parts that commonly fix it
Always match the part number to your exact model.
Coil cleaner
For clearing dirt and debris from the outdoor coil, one of the airflow causes Fujitsu lists.
Search eBay →Compressor temperature thermistor
Replace only if it measures out of range on Fujitsu's resistance chart; match your outdoor unit model number.
Search eBay →Refrigerant leak detector
For a technician to find a leak before recharging; low refrigerant is one of Fujitsu's listed A3 causes.
Search eBay →Multimeter
For a technician checking the thermistor's resistance against Fujitsu's chart.
Search eBay →Sources
- Fujitsu AOUH18/24LPAS1 service manual, 2-25 E: A3 Compressor temperature error (Outdoor unit): 226 °F (108 °C) protection stop twice in 24 hours, forecast of cause and check points 1 to 6
- Fujitsu 410A mini-split troubleshooting guide (2019), A3 Compressor temperature error: Operation 10, Timer 3, Economy continuous; check 3-way valve, EEV, strainer, outdoor fan, heat exchanger, compressor thermistor, refrigerant
- Fujitsu AUXG07KVLA service manual, 2-40 E: A3 Compressor temperature error (Outdoor unit) (ManualsLib, page 219)
Last reviewed 2026-10-24. Always confirm against the manual for your exact model number.