Daikin Aircon Blinking Light Patterns

Reference table for common Daikin blink patterns. Use this to identify likely fault classes and narrow what to check next.

Before you use this tool

This is a blink-pattern guidance table, not a model-exact diagnosis. Pattern meaning can vary by controller and series. If your controller shows a direct code (for example `CH21`, `U4`, `E6`), use the error-code guide for a faster match.

Safety warning

Stop using the unit and contact a technician if the breaker trips repeatedly, you smell burning, see sparks, hear loud electrical buzzing, or water is leaking from places it normally should not.

Daikin pattern table

Includes common SG residential blinking-light patterns with likely fault classes and typical causes.

Continuous or repeating blink

Indoor indicator blinks in a repeating fault pattern and diagnosis returns communication fault

Indoor-outdoor transmission fault indication

Details

Pattern ID: GREEN_BLINK_COMMUNICATION_U4

Pattern type: Persistent blink

Service code (reference only): U4

Category: Communication

Indicator: Indoor unit

LEDs: GREEN, OPERATION

Typical causes

Loose indoor-outdoor interconnection wiring
Terminal contact or wiring joint issue
Indoor or outdoor PCB communication fault

Continuous or repeating blink

Operation indicator blinks quickly during a defrost/protection cycle

Fast green blink can indicate temporary defrost operation

Details

Pattern ID: GREEN_FAST_BLINK_DEFROST

Pattern type: Persistent blink

Category: System

Indicator: Indoor unit

LEDs: GREEN, OPERATION

Typical causes

Outdoor coil defrost cycle
Temporary protection control sequence
Cold-weather operation transition

Continuous or repeating blink

Operation indicator shows a slow green blink while the unit is in standby or startup sequence

Slow green blink is commonly described as startup/standby behavior on some Daikin units

Details

Pattern ID: GREEN_SLOW_BLINK_STANDBY

Pattern type: Persistent blink

Category: System

Indicator: Indoor unit

LEDs: GREEN, OPERATION

Typical causes

Unit is powered and preparing to run
Control logic is waiting for load demand
Model-specific normal indicator behavior

Continuous or repeating blink

OPERATION lamp keeps blinking after a restart attempt

Persistent OPERATION-lamp blinking indicates a stored malfunction that needs diagnosis

Details

Pattern ID: OP_LAMP_BLINK_PERSISTENT_FAULT

Pattern type: Persistent blink

Category: System

Indicator: Indoor unit

LEDs: OPERATION

Typical causes

Protection trip did not clear
Sensor/control abnormality
Indoor or outdoor control fault

Blink count: 1

Red indicator flashes once repeatedly

Single red flash is described as an indoor-side sensor/control warning on SG service content

Details

Pattern ID: RED_1_FLASH_SENSOR_WARNING

Pattern type: Blink count cycle

Blink count: 1

Category: Sensor

Indicator: Indoor unit

LEDs: RED

Typical causes

Indoor sensor signal abnormality
Sensor connector contact issue
Control-board input instability

Blink count: 2

Red indicator flashes two times repeatedly

Two red flashes are described as an outdoor-side fault warning

Details

Pattern ID: RED_2_FLASH_OUTDOOR_WARNING

Pattern type: Blink count cycle

Blink count: 2

Category: Outdoor

Indicator: Indoor unit

LEDs: RED

Typical causes

Outdoor control issue
Inter-unit wiring fault
Outdoor protection trip condition

Blink count: 3

Red indicator flashes three times repeatedly

Three red flashes are described as compressor-side abnormality warning

Details

Pattern ID: RED_3_FLASH_COMPRESSOR_WARNING

Pattern type: Blink count cycle

Blink count: 3

Category: Inverter

Indicator: Indoor unit

LEDs: RED

Typical causes

Compressor overload/protection event
Inverter drive stress condition
Refrigerant-side pressure abnormality

Run remote self-check

In diagnosis mode, cycling codes until a long beep confirms the matching fault code

Remote self-diagnosis workflow used after indicator blinking

Details

Pattern ID: REMOTE_DIAG_LONG_BEEP_MATCH

Pattern type: Code-check flow

Category: General

Indicator: Remote

LEDs: DISPLAY

Typical causes

Unit has a stored fault condition
User initiated fault-code check
Code confirmation needed before service

Continuous or repeating blink

Yellow/orange indicator blinks as maintenance or drainage warning

Maintenance/drainage alert pattern described on SG service pages

Details

Pattern ID: YELLOW_ORANGE_BLINK_MAINTENANCE

Pattern type: Persistent blink

Category: General

Indicator: Indoor unit

LEDs: YELLOW, ORANGE

Typical causes

Dirty or blocked filters
Drainage blockage/water backup
Model-specific maintenance reminder

Not sure how to read your Daikin blink pattern?

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