What causes Fujitsu Mini Split A1?

Low refrigerant charge or a refrigerant leak. With too little refrigerant the compressor runs hot, and Fujitsu's support checklist starts with checking running pressures for a low charge. A 2-way or 3-way service valve that is closed or not fully open, often after a new install. Fujitsu's first check is whether the 3-way valve is open. A failed electronic expansion valve (EEV), capillary tube or clogged strainer that restricts refrigerant flow. Poor heat transfer at the outdoor unit: a failed outdoor fan motor, a fan that won't turn, or debris and dirt on the outdoor coil. A failed discharge temperature thermistor giving a false high reading. A failed outdoor main control board, which Fujitsu lists last.

How do I fix Fujitsu Mini Split A1?

Confirm the code. On lamp-only models count the flashes: 10 Operation flashes and 1 Timer flash is A1 on most current Fujitsu series. Write it down for your technician. Turn the unit off and switch off its breaker or pull the outdoor disconnect for about 5 minutes, then restore power. Fujitsu's support checklist says the code should reset; if it comes back, the cause needs a technician. With the power off, look at the outdoor unit. Clear leaves, grass, snow or anything blocking the coil. Check that the outdoor fan isn't blocked by debris. Don't reach into the unit; just look through the grille. Clean or replace the indoor unit's air filters, since poor airflow makes the system work harder. If the system was installed recently, call the installer first. A closed service valve or a missing refrigerant charge for a long line set is an installation problem and is usually covered.

When should I call a pro for Fujitsu Mini Split A1?

A1 returns after a power reset. A technician checks that the 2-way and 3-way service valves are fully open, which is the first item in Fujitsu's service manual. The valves are open. The technician puts gauges on in cooling mode; Fujitsu's support checklist says suction pressures well below about 110 to 130 PSI point to a low charge or a leak, which must be found and repaired before the charge is weighed back in. The charge is right. The technician checks the expansion valve coil and strainer for a restriction, and checks the outdoor fan motor and coil. Everything mechanical checks out. The discharge thermistor is unplugged from the board and measured against Fujitsu's resistance chart, and replaced if it's out of range. If none of these fixes it, Fujitsu's last step is replacing the outdoor main board.

Code: A1🔧 Fujitsu Mini Split

Fujitsu Mini Split Error Code A1: Discharge Temperature Error (Meaning, Causes, Fixes)

Q: What does Fujitsu Mini Split A1 mean?

A1 on a Fujitsu mini split is a discharge temperature error: the gas leaving the compressor got too hot, so the outdoor unit shut the compressor down to protect it. Fujitsu sets A1 when that protective stop at 230 °F (110 °C) or more happens twice within 24 hours. The most common causes are low refrigerant from a leak, a service valve left closed, a stuck expansion valve or clogged strainer, poor outdoor airflow, or a bad discharge temperature sensor. Fujitsu's service manuals list A1 as "Discharge temperature error (Outdoor unit)". The outdoor main board watches a thermistor (a temperature-sensing resistor) on the compressor's discharge line, and stops the compressor when the discharge temperature reaches 230 °F (110 °C) or more while it runs. If that protection stop happens twice within 24 hours, the unit locks out with A1. On wired remotes A1 shows as a code (some show it as 00:A1); on units with indicator lamps, many current Fujitsu series (for example LMAS, LZAS, LPAS, RLS3, RL2 and RLF) show it as the Operation lamp flashing 10 times and the Timer lamp once, with the Economy lamp flashing continuously. Some older series use a different pattern, such as 7 Operation flashes and 2 Timer flashes on RLS, RLX and RLXS models, so check the blink chart for your series.

Reviewed 2026-10-24 · Based on 3 manufacturer & service sources

What the code means

Fujitsu's service manuals list A1 as "Discharge temperature error (Outdoor unit)". The outdoor main board watches a thermistor (a temperature-sensing resistor) on the compressor's discharge line, and stops the compressor when the discharge temperature reaches 230 °F (110 °C) or more while it runs. If that protection stop happens twice within 24 hours, the unit locks out with A1. On wired remotes A1 shows as a code (some show it as 00:A1); on units with indicator lamps, many current Fujitsu series (for example LMAS, LZAS, LPAS, RLS3, RL2 and RLF) show it as the Operation lamp flashing 10 times and the Timer lamp once, with the Economy lamp flashing continuously. Some older series use a different pattern, such as 7 Operation flashes and 2 Timer flashes on RLS, RLX and RLXS models, so check the blink chart for your series.

Likely causes

Low refrigerant charge or a refrigerant leak. With too little refrigerant the compressor runs hot, and Fujitsu's support checklist starts with checking running pressures for a low charge.
A 2-way or 3-way service valve that is closed or not fully open, often after a new install. Fujitsu's first check is whether the 3-way valve is open.
A failed electronic expansion valve (EEV), capillary tube or clogged strainer that restricts refrigerant flow.
Poor heat transfer at the outdoor unit: a failed outdoor fan motor, a fan that won't turn, or debris and dirt on the outdoor coil.
A failed discharge temperature thermistor giving a false high reading.
A failed outdoor main control board, which Fujitsu lists last.

Safe DIY checks

⚠ Before you start

Turn off power at the breaker or outdoor disconnect before inspecting the unit. Inverter mini splits store a dangerous charge in their capacitors after power is off, and the compressor discharge line can be hot enough to burn. Refrigerant work requires an EPA-certified technician, and leak repair, nitrogen pressure testing and recharging should be left to a licensed HVAC pro.

Confirm the code. On lamp-only models count the flashes: 10 Operation flashes and 1 Timer flash is A1 on most current Fujitsu series. Write it down for your technician.
Turn the unit off and switch off its breaker or pull the outdoor disconnect for about 5 minutes, then restore power. Fujitsu's support checklist says the code should reset; if it comes back, the cause needs a technician.
With the power off, look at the outdoor unit. Clear leaves, grass, snow or anything blocking the coil.
Check that the outdoor fan isn't blocked by debris. Don't reach into the unit; just look through the grille.
Clean or replace the indoor unit's air filters, since poor airflow makes the system work harder.
If the system was installed recently, call the installer first. A closed service valve or a missing refrigerant charge for a long line set is an installation problem and is usually covered.

🛠 When to call a pro

A1 returns after a power reset. A technician checks that the 2-way and 3-way service valves are fully open, which is the first item in Fujitsu's service manual.
The valves are open. The technician puts gauges on in cooling mode; Fujitsu's support checklist says suction pressures well below about 110 to 130 PSI point to a low charge or a leak, which must be found and repaired before the charge is weighed back in.
The charge is right. The technician checks the expansion valve coil and strainer for a restriction, and checks the outdoor fan motor and coil.
Everything mechanical checks out. The discharge thermistor is unplugged from the board and measured against Fujitsu's resistance chart, and replaced if it's out of range. If none of these fixes it, Fujitsu's last step is replacing the outdoor main board.

Parts that commonly fix it

Always match the part number to your exact model.

⚙

Refrigerant leak detector

For a technician to find the leak before the system is recharged; low charge is a common A1 cause.

Search eBay →

⚙

Discharge temperature thermistor

Replace only if it measures out of range on Fujitsu's resistance chart; match your outdoor unit model number.

Search eBay →

⚙

Coil cleaner

For a dirty outdoor coil, which Fujitsu lists among the A1 checks.

Search eBay →

Sources

Last reviewed 2026-10-24. Always confirm against the manual for your exact model number.

Fujitsu Mini Split Error Code A1: Discharge Temperature Error (Meaning, Causes, Fixes)

What the code means

Likely causes

Safe DIY checks

🛠 When to call a pro

Parts that commonly fix it

Refrigerant leak detector

Discharge temperature thermistor

Coil cleaner

Related codes

Sources