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Daikin Error Codes & Fault Codes

Complete alphanumeric error code reference for Daikin mini-split and VRF systems. Bookmark this page for quick field lookups.

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CodeDescription
A1Indoor PCB defective
A3Drain level control malfunction
A5Freeze up / overheat protection
C4Heat exchanger temp sensor fault
E1Outdoor PCB error
E3High pressure switch activated
E5Compressor overcurrent
F3Discharge pipe temperature too high
F6Refrigerant overcharge
U0Low refrigerant / shortage
U4Communication error (MOST COMMON)

Detailed Code Reference

A1
Indoor PCB defective
Cause: Failed indoor control board
Fix: Replace indoor PCB
A3
Drain level control malfunction
Cause: Clogged drain or failed float switch
Fix: Clear drain line, check float switch
A5
Freeze up / overheat protection
Cause: Low airflow, dirty filter, or low charge
Fix: Clean filters, check refrigerant charge, verify airflow
C4
Heat exchanger temp sensor fault
Cause: Open or short in thermistor
Fix: Test thermistor, replace if out of spec
E1
Outdoor PCB error
Cause: Failed outdoor board
Fix: Replace outdoor PCB
E3
High pressure switch activated
Cause: Dirty condenser, fan failure, or overcharge
Fix: Clean condenser, check fan motor, verify charge
E5
Compressor overcurrent
Cause: Failing compressor, low voltage, or high head pressure
Fix: Check voltage and amperage, address high pressure cause
F3
Discharge pipe temperature too high
Cause: Low charge, restriction, or compressor valve issue
Fix: Check charge, check for restrictions, test compressor valves
F6
Refrigerant overcharge
Cause: Too much refrigerant
Fix: Recover excess refrigerant to manufacturer specs
U0
Low refrigerant / shortage
Cause: Leak in system or undercharge
Fix: Leak test entire system, repair leak and recharge
U4
Communication error (MOST COMMON)
Cause: Wiring fault, board failure, or connector issue
Fix: Check all communication wiring, re-seat connectors, power cycle system

Frequently Asked Questions

What does Daikin error code U4 mean?

Daikin U4 is the most common error code and indicates a communication error between the indoor and outdoor units. This is typically caused by a wiring fault, loose connector, or board failure. Start by checking all communication wiring connections, re-seating connectors, and power cycling the entire system.

What does Daikin error code U0 mean?

Daikin U0 indicates low refrigerant or a refrigerant shortage in the system. This means there is likely a leak. You should leak test the entire system, repair any leaks found, and recharge to the manufacturer specification on the data plate.

What does Daikin error code E3 mean?

Daikin E3 means the high pressure switch has activated. Common causes include a dirty condenser coil, failed outdoor fan motor, or refrigerant overcharge. Clean the condenser coil, verify the fan motor is running, and check the refrigerant charge.

How do I read Daikin error codes?

Daikin uses alphanumeric error codes displayed on the indoor unit or wired remote. Codes starting with A indicate indoor unit faults, C indicates sensor faults, E indicates outdoor unit faults, F indicates refrigerant circuit issues, and U indicates system/communication errors.

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