Fujitsu Mini Split Error Codes: Reading the Blinking Lights

Read the lights before anything else

Green Operation light flashing on its own, in heating. A defrost. Fujitsu says the indoor unit stops for between 7 and 15 minutes while the outdoor unit clears its frost, and the Operation light flashes until it is done: what a mini split does on heat that looks like a fault.

Operation light flashing on one room of a multi zone system. Two rooms are asking for different modes. Fujitsu says heating with cooling or dry, or heating with fan, puts one unit on standby and flashes its Operation light. Set every room to the same mode.

Orange Timer light flashing on its own, after a power cut. Fujitsu says a power cut during a timer resets it, and the Timer light flashes to tell you. Set the timer again: bringing the system back after a power cut.

Green Economy light flashing on its own. The filter reminder, which works only if the installer switched it on. Clean the filters, then press the Manual Auto button on the indoor unit for 2 seconds or less to reset it.

Operation and Timer counting, Economy flashing fast. A fault code. The next section turns it into a number.

Count both lights

First digit: the Operation light. Count its flashes between pauses.

Second digit: the Timer light. Count its flashes the same way. On Fujitsu’s newer wall units the Economy light flashes continuously the whole time, and that is what tells you it is a code.

Ten flashes is the letter A. Ten on Operation and one on Timer is code A1. Three on Operation and ten on Timer is 3A.

A wired controller or the app. A wired wall controller shows the code directly. Fujitsu’s guide lists the FGLair app codes with a decimal, such as 11.1 or 62.2, and the part before the point is the same code.

Work the owner checks, power off first

11, the units not talking. Make sure the outdoor unit has power: its breaker in the panel and the disconnect switch beside it. Fujitsu’s next step is the wiring and voltage between the units, which is a technician’s meter job.

The outdoor unit’s air, 65, 94, A1 and A3. Fujitsu’s checks for these start with the outdoor fan and coil. Clear leaves, snow and anything stacked close to the unit, and rinse a matted coil gently: how to rinse an outdoor coil without bending the fins.

The outdoor fan, 97 and 98. Fujitsu’s code means the blade turned under 100 rpm after starting. With the breaker off, look for a stick, leaves or ice stopping it.

The indoor fan, 51. The fan ran under a third of the speed it was asked for. With the power off, look through the outlet for anything caught in the long fan wheel.

The Manual Auto button, 35. Fujitsu’s code means the button read as pressed for a full minute. Make sure nothing is pressing on it and that it springs back.

A power reset, 62, 86 and J2. Fujitsu’s first step for these is to reset the power. For 86 it says to leave it off for 3 to 5 minutes.

The drain hose, 53. On units with a drain pump, Fujitsu’s list ends with checking the drain hose for blockages: where a mini split’s water goes and how it backs up.

Know when to stop

11 that survives a power reset. Fujitsu’s check is the wiring from the panel to the outdoor unit and on to the indoor unit, with the voltage measured at each. It adds that wire nuts and splices are not recommended in that cable.

The sensor codes, 41, 42 and 71 to 77. Each is a sensor read as open or shorted, checked against Fujitsu’s resistance chart. Usually the sensor, sometimes the board.

A1, A3, A5 and 99. Fujitsu’s checks include the service valves, the expansion valve, the strainer and the refrigerant charge with a leak test. That is sealed system work for a licensed technician: signs the refrigerant is leaking.

23, 26, 29 and the multi zone setup codes. These are installation problems with pairing, addressing or wiring. The installer should come back.