Daikin Mini Split Blinking Light: A1, C9 & Error Codes

A Daikin mini split blinking light needs a model-specific check. First record the indoor unit, outdoor unit and controller model numbers, then retrieve the displayed error code using the matching manual. A light pattern alone is not enough to choose a replacement part.

Accuracy review: September 11, 2026. Independent homeowner guide.

Jump to: Read the code · A1, C9 and other codes · Owner checks · Service checklist · FAQs

Start with your model and controller

Photograph accessible equipment labels without removing electrical covers. Include the full model suffix; two units with similar names may need different instructions. Use Daikin’s Owner Support Center to find your documentation, or ask your installer for the matching operation manual.

Scope of the code table below: Daikin manual SiUS121502E covers 2MXS18NMVJU, 3MXS24NMVJU and 4MXS36NMVJU systems. For compatible CTXS, FTXS, FDXS, CDXS and FVXS indoor units, check the exact model in the manual’s applied-model list. FFQ units have a separate diagnostic section.

ARC452 or ARC466 remote: retrieve the code

For the covered controllers, hold timer CANCEL for about five seconds until 00 appears. Aim at the indoor unit and press CANCEL repeatedly; record the code accompanied by a long beep. Short or double beeps do not identify the matching fault. See ARC452 instructions, printed page 102 or ARC466 instructions, printed page 105.

If your remote has different buttons, is a wired controller, or does not respond as described, stop and use its own instructions. Take a photo of any displayed code before attempting a restart.

What A1, C9 and other Daikin codes mean

These are diagnostic categories for the models above, not a universal blink-count chart. Source: Daikin SiUS121502E, printed pages 114–115 (Daikin-authored PDF hosted by Rogers Supply).

Code	Meaning in this manual
A1	Indoor control-board abnormality
C9	Room-temperature sensor circuit abnormality
A5	Freeze protection or heating peak limitation
A6	Indoor fan motor or associated fault
U4	Indoor/outdoor communication fault
E1	Outdoor control-board abnormality
U0	Refrigerant-shortage indication
L5	Inverter output overcurrent

Do not order a board, sensor or compressor from a code alone. Ask the technician to confirm the cause with the applicable diagnostic procedure before authorizing a replacement.

Could blinking mean a heating/cooling mode conflict?

Yes, on some multi-room systems. For example, the separate FTXS15/18/24WVJU9 operation manual, printed page 39, distinguishes blinking roughly every 2–3 seconds for a mode conflict from approximately 0.5-second blinking for a fault. Follow that manual’s mode-setting and code-reading steps if your model matches.

This example is for the W-series models named in that operation manual. Do not apply its timing to every Daikin system or translate one, two or three flashes into an A1 or C9 code.

Safe checks you can make before a service visit

Record what happened. Note the room, operating mode, set temperature, displayed code and whether one indoor unit or the whole system is affected. A short video of the light can help the technician.
Check ordinary settings. On a multi-room installation, note what modes the other rooms are using. Follow your model’s instructions if they identify a mode conflict.
Check accessible airflow paths. Move furniture or curtains away from air openings. Clean removable filters only as your operation manual directs, with the equipment stopped and power isolated as instructed. Do not open electrical compartments.
Report ice, water or repeated shutdowns. Stop operation if there is unusual icing or leakage. These observations are useful evidence; they do not establish the refrigerant charge or prove a leak.
Arrange service for a recurring fault. Avoid repeated breaker cycling. A restart is not a repair, and a disappearing light does not confirm that the underlying problem is resolved.

Stop using the equipment if you notice smoke, a burning smell, damaged wiring or repeated breaker trips. Keep clear of electrical parts and obtain professional help. Wiring tests, internal sensor measurements, board work and refrigerant service belong with a qualified HVAC technician.

A checklist to send your technician

Copy this into your service request to help the technician arrive prepared:

Indoor model and serial number:
Outdoor model and serial number:
Controller model:
Exact displayed code and how it was retrieved:
Which rooms are affected and their operating modes:
When the problem started; any recent outage, installation or service:
Photos/video of the light, display and accessible labels:
Any ice, water, unusual noise or breaker trips:

Request a diagnosis and written estimate before approving parts. Ask whether any warranty coverage applies. Use Daikin’s contractor finder if you need a service provider.

Frequently asked questions

Can I diagnose the problem by counting flashes?

Use the procedure for your exact model and controller. The code table above uses displayed alphanumeric codes; it does not assign codes to a number of flashes.

Should I add refrigerant when the light blinks?

No. A blinking light, weak cooling or visible ice is not enough to establish the charge. Give the technician the code and symptoms and request a diagnosis before any refrigerant work.

Will a 30-second breaker reset fix it?

There is no single reset duration or guaranteed cure for every Daikin mini split. Follow the operation manual for your equipment. If the fault returns, stop repeating resets and arrange service.

How much will the repair cost?

The code alone cannot establish a repair price. Ask for a written estimate that separates diagnosis, labor, parts and any refrigerant work, and check warranty coverage before agreeing to the repair.