Daikin Error Codes: Full List and How to Fix Them

When your Daikin AC shows a code like U0, A5, or E3, it is not random. It is a built-in diagnostic system pointing to a specific problem.

Some codes indicate minor issues you can fix in minutes. Others signal serious failures that require professional repair.

Our guide covers all major Daikin error codes, what they mean, what causes them, and what you should do next.

If your system is not working and you need immediate help, contact HVAC Services.

How Daikin Error Codes Work

Daikin uses a letter and number system. The letter tells you where the issue is.

Code Categories

• A codes: indoor unit issues
• C codes: sensors and thermistors
• E codes: outdoor unit problems
• U codes: communication and refrigerant
• L and P codes: inverter and power

This structure helps you narrow down the problem quickly.

Full Daikin Error Codes Table

Code	Category	Meaning	Symptoms	Root Cause	Fix Difficulty	Recommended Action
A0	Indoor	General protection fault	System shuts down	Internal system error	Hard	Full system diagnosis
A1	Indoor	PCB error	Unit not responding	Control board failure	Hard	Replace PCB
A3	Indoor	Drain error	Water leak, unit stops	Clogged drain line	Easy	Clean drain line
A5	Indoor	Coil temperature issue	Weak cooling, ice buildup	Dirty filter or low airflow	Easy	Clean filter, check airflow
A6	Indoor	Fan motor fault	No airflow	Motor failure	Hard	Repair or replace motor
A7	Indoor	Louver motor error	Air direction not working	Mechanical jam	Medium	Inspect and fix
A9	Indoor	Expansion valve error	Poor cooling	Valve malfunction	Hard	Call technician
C4	Sensor	Coil sensor error	Irregular cooling cycles	Faulty thermistor	Medium	Replace sensor
C5	Sensor	Pipe sensor error	System instability	Wiring or sensor issue	Medium	Repair wiring
C9	Sensor	Air sensor error	Incorrect temperature reading	Sensor failure	Easy	Inspect or replace
E1	Outdoor	PCB error	Outdoor unit not running	Board failure	Hard	Replace PCB
E3	Outdoor	High pressure	System overheating	Dirty condenser	Medium	Clean condenser
E4	Outdoor	Low pressure	No cooling	Refrigerant leak	Hard	Repair leak and recharge
E5	Outdoor	Compressor overload	Random shutdowns	Overheating	Hard	Diagnose system
E6	Outdoor	Compressor lock	Loud noise or no start	Mechanical failure	Critical	Replace compressor
E7	Outdoor	Fan motor error	Outdoor overheating	Fan failure	Hard	Repair motor
U0	System	Low refrigerant	Weak cooling	Refrigerant leak	Hard	Leak repair
U2	System	Power supply error	Unit resets	Voltage instability	Medium	Check electrical supply
U4	System	Communication error	Units not syncing	Wiring or PCB issue	Hard	Diagnose wiring
U8	System	System conflict	Control issues	Configuration error	Easy	Reset system
L5	Inverter	Overload	System stops	Electrical stress	Hard	Repair inverter
L8	Inverter	Overheating	Reduced performance	Poor airflow	Easy	Clean system
P1	Power	Voltage protection	Unit shuts off	Power fluctuation	Medium	Check voltage
P4	Power	Inverter temp error	Overheating	Cooling failure	Hard	Service required

A-Сodes: Indoor Unit Errors

A0 – General Protection Fault

The system has shut down due to a critical issue.

Causes

• Internal fault
• Sensor conflict
• Electrical issue

What to do

• Restart the unit
• If the code returns, call a technician

Check out our detailed guide on Daikin A0 error.

A1 – Indoor PCB Error

Failure of the control board inside the indoor unit.

Causes

• Power surge
• Component failure

What to do

• Requires professional repair or replacement

We have a complete guide on Daikin A1 error.

A3 – Drain System Error

Water is not draining properly.

Causes

• Clogged drain line
• Blocked pump

What to do

• Clean the drain line
• Check for blockages

Read our complete guide on Daikin A3 error.

A5 – Coil Temperature Protection

The indoor coil temperature is outside normal range.

Causes

• Dirty air filter
• Frozen coil
• Low airflow

What to do

• Clean or replace filter
• Check airflow
• If persists, check refrigerant

You can read out more in our Daikin A5 error code guide.

A6 – Fan Motor Fault

Indoor fan is not operating correctly.

Causes

• Motor failure
• Capacitor issue

What to do

• Requires repair

We have a complete A6 & A7 Daikin Error Codes guide.

A7 – Louver Motor Error

Air direction flaps are not moving.

Causes

• Motor jam
• Mechanical blockage

What to do

• Inspect for obstruction
• May require repair

A9 – Expansion Valve Error

Electronic expansion valve malfunction.

Causes

• Valve failure
• Control issue

What to do

• Professional diagnosis required

See our full guide on Daikin A9 HVAC error code fix.

C-Codes: Sensor Errors

C4 – Heat Exchanger Sensor Error

Indoor coil sensor malfunction.

Causes

• Faulty thermistor
• Wiring issue

What to do

• Replace sensor

C5 – Pipe Sensor Error

Pipe temperature sensor failure.

Causes

• Damaged wiring
• Sensor fault

What to do

• Repair or replace sensor

C9 – Air Temperature Sensor Error

Return air sensor is not working correctly.

Causes

• Sensor degradation
• Loose connection

What to do

• Inspect and replace if needed

E-Codes: Outdoor Unit Errors

E1 – Outdoor PCB Error

Control board failure in outdoor unit.

What to do

• Requires repair or replacement

E3 – High Pressure Protection

System pressure is too high.

Causes

• Dirty condenser coil
• Blocked airflow

What to do

• Clean outdoor unit
• Ensure proper ventilation

E4 – Low Pressure Error

System pressure is too low.

Causes

• Refrigerant leak
• Undercharge

What to do

• Requires leak detection and recharge

E5 – Compressor Overload

Compressor is under excessive load.

Causes

• High temperature
• Electrical issue

What to do

• Professional service required

E6 – Compressor Lock

Compressor is not starting or is seized.

Causes

• Mechanical failure
• Electrical fault

What to do

• Major repair or replacement

E7 – Outdoor Fan Motor Error

Outdoor fan is not functioning properly.

Causes

• Motor failure
• Wiring issue

What to do

• Repair or replace motor

U-Codes: System And Communication Errors

U0 – Low Refrigerant

Insufficient refrigerant in the system.

Causes

• Leak in the system

Symptoms

• Weak or no cooling

What to do

• Leak repair and recharge required

Check out our full guide on Daikin U0 error code fix.

U2 – Power Supply Error

Voltage is outside acceptable range.

Causes

• Electrical instability
• Wiring issue

What to do

• Check power supply
• May need electrician

U4 – Communication Error

Indoor and outdoor units are not communicating.

Causes

• Wiring fault
• PCB issue

What to do

• Requires diagnosis

U8 – System Conflict

Controller or configuration mismatch.

Causes

• Incorrect setup
• Multiple controllers conflict

What to do

• Reset system
• Reconfigure controls

L- and P-Codes: Inverter And Power Errors

L5 – Inverter Overload

Inverter is overloaded or overheating.

Causes

• Electrical issue
• Compressor strain

What to do

• Professional repair required

L8 – Electrical Overheating

Electrical components are overheating.

Causes

• Poor airflow
• High ambient temperature

What to do

• Improve ventilation
• Inspect system

P1 – Voltage Protection

Voltage is too high or too low.

What to do

• Check power supply

P4 – Inverter Temperature Error

Inverter is overheating.

Causes

• Cooling failure
• Blocked airflow

What to do

• Requires service

How to diagnose Daikin error codes

Step 1: Identify the code type

Use the first letter to locate the issue area.

Step 2: Check simple issues

• Dirty filter
• Power reset
• Blocked airflow

Step 3: Look for symptoms

• Ice on coil
• No cooling
• Unusual noise

Step 4: Decide next action

Safe to fix yourself

• Filter cleaning
• Drain cleaning
• Basic reset

Call a technician

• Refrigerant issues
• Electrical faults
• Compressor problems

Daikin Repair Cost

Problem Type	Related Codes	Repair Type	Cost Range	Urgency	Notes
Drain cleaning	A3	Cleaning	$75–$200	Low	Common DIY
Filter / airflow	A5, L8	Maintenance	$0–$150	Low	Often ignored
Sensor replacement	C4, C5, C9	Replace sensor	$150–$350	Medium	Quick fix
Fan motor repair	A6, E7	Motor repair	$300–$700	Medium	Parts + labor
Refrigerant recharge	U0, E4	Leak + refill	$300–$900	High	Must fix leak
PCB replacement	A1, E1	Board replace	$400–$1200	High	Expensive
Communication repair	U4	Wiring / board	$200–$800	High	Hard to diagnose
Inverter repair	L5, P4	Electrical repair	$500–$1500	High	Complex
Compressor repair	E5	Repair	$800–$2000	Critical	Risky
Compressor replacement	E6	Replace	$1500–$3000	Critical	Often not worth it

Final Takeaway

• Not all error codes are equal
• Some are quick fixes, others are expensive failures
• Ignoring codes → higher repair costs

The faster you diagnose, the cheaper the fix.