Daikin FTK(X)B wall-mount mini-splits error codes

15 heat pump / mini-split error codes for Daikin FTK(X)B wall-mount mini-splits, what each one means and what to try, paraphrased from Daikin's own source. Codes vary by model, so confirm in your own manual.

Safety. The service manual warns to disconnect power before repairs (electric shock risk) and not to touch leaking refrigerant (frostbite). Repairs are for a qualified technician. Source: Service Manual, Inverter Wall Mounted Single Split FTK(X)B / RK(X)B (Daikin).

All codes

A1 Indoor PCB abnormality.
A5 Antifreeze protection or high pressure control.
A6 Indoor fan motor fault.
C4 Indoor heat exchanger thermistor fault.
C9 Indoor room thermistor fault.
E1 Outdoor PCB abnormality.
E5 Compressor overload.
E6 Compressor lock or start-up abnormality.
E7 Outdoor fan motor locked.
E8 AC input over current.
F3 Discharge pipe overheating.
H6 Compressor position sensor fault.
U0 Insufficient gas.
U2 DC voltage out of range.
U4 Communication abnormality.

A1

What it means: Indoor PCB abnormality. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

A5

What it means: Antifreeze protection or high pressure control. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

A6

What it means: Indoor fan motor fault. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

C4

What it means: Indoor heat exchanger thermistor fault. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

C9

What it means: Indoor room thermistor fault. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

E1

What it means: Outdoor PCB abnormality. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

E5

What it means: Compressor overload. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

E6

What it means: Compressor lock or start-up abnormality. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

E7

What it means: Outdoor fan motor locked. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

E8

What it means: AC input over current. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

F3

What it means: Discharge pipe overheating. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

H6

What it means: Compressor position sensor fault. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

U0

What it means: Insufficient gas. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

U2

What it means: DC voltage out of range. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

U4

What it means: Communication abnormality. This one often needs a licensed technician.

What to try

Have a qualified technician service it.

Source

Service Manual, Inverter Wall Mounted Single Split FTK(X)B / RK(X)B (Daikin) (checked 2026-11-02)

Brand names and model names are trademarks of their owners. Costolio is not affiliated with or endorsed by any manufacturer.

Source checked 2026-11-02