Daikin Aircon C4 Error Code: What It Means for Your Model

What does Daikin C4 mean?

Daikin C4 is listed as faulty heat exchanger temperature sensor, malfunction of liquid pipe thermistor for heat exchanger, and indoor heat-exchanger liquid-pipe thermistor abnormality in mixed model-family source rows, including VRV X RXQ-A(N)R cooling only, VRV 5-S RXYSA R32, VRV 5 Heat Recovery REMA / REYA R32, VRV 5 Heat Pump RYMA / RXYA R32, EKVDX / VAM R32 ventilation, Sky Air FNA R32 - indoor error overview, and EKEA / EKEXVA AHU control box. The loaded row is source-backed by official diagnostic material. Do not collapse this code across model families; use the model, series, or system type to choose the right row. Confirm the exact model, series, or signal row before accepting a parts quote.

Choose the matching source row

The same visible code has more than one source-backed meaning. Match the model family, system type, or reporting unit before approving parts.

Code, what it means, and what to check first
Code	What it means	What to check first
EZi	Faulty heat exchanger temperature sensor	Match this row to the installed model or reporting unit, then use the source-specific checks below.
Fan Coil	Malfunction of liquid pipe thermistor for heat exchanger	Match this row to the installed model or reporting unit, then use the source-specific checks below.
VRV X RXQ-A(N)R cooling only	Indoor heat-exchanger liquid-pipe thermistor abnormality	Match this row to the installed model or reporting unit, then use the source-specific checks below.
VRV 5-S R32 - C4 / VRV 5 Heat Recovery R32 - C4 / VRV 5 Heat Pump R32 - C4	Indoor liquid heat-exchanger thermistor malfunction	Record the displayed code, unit type, and serial number for qualified diagnosis.
EKVDX / VAM R32 ventilation - C4	Liquid-pipe heat-exchanger thermistor malfunction	Match the EKVDX and paired VAM model, then use the project service manual for diagnosis.
Sky Air FNA R32 - C4 (indoor error overview)	Liquid-pipe thermistor malfunction	Confirm the indoor model is FNA25~60A2VEB(9), record the reporting controller, and follow the matching Daikin service procedure.
EKEA / EKEXVA AHU control box	Heat-exchanger liquid-pipe thermistor malfunction	Match this row to the installed model or reporting unit, then use the source-specific checks below.

Code
EZi
What it means
Faulty heat exchanger temperature sensor
What to check first
Match this row to the installed model or reporting unit, then use the source-specific checks below.
Code
Fan Coil
What it means
Malfunction of liquid pipe thermistor for heat exchanger
What to check first
Match this row to the installed model or reporting unit, then use the source-specific checks below.
Code
VRV X RXQ-A(N)R cooling only
What it means
Indoor heat-exchanger liquid-pipe thermistor abnormality
What to check first
Match this row to the installed model or reporting unit, then use the source-specific checks below.
Code
VRV 5-S R32 - C4 / VRV 5 Heat Recovery R32 - C4 / VRV 5 Heat Pump R32 - C4
What it means
Indoor liquid heat-exchanger thermistor malfunction
What to check first
Record the displayed code, unit type, and serial number for qualified diagnosis.
Code
EKVDX / VAM R32 ventilation - C4
What it means
Liquid-pipe heat-exchanger thermistor malfunction
What to check first
Match the EKVDX and paired VAM model, then use the project service manual for diagnosis.
Code
Sky Air FNA R32 - C4 (indoor error overview)
What it means
Liquid-pipe thermistor malfunction
What to check first
Confirm the indoor model is FNA25~60A2VEB(9), record the reporting controller, and follow the matching Daikin service procedure.
Code
EKEA / EKEXVA AHU control box
What it means
Heat-exchanger liquid-pipe thermistor malfunction
What to check first
Match this row to the installed model or reporting unit, then use the source-specific checks below.

What to do now

Use these steps to record evidence and match the installed model to its service manual before diagnosis or a repair quote.

Record C4 and match the service manual
Record C4 and stop there; the source table gives no customer reset procedure. Arrange diagnosis with the matching service manual.
No manufacturer reset steps listed for C4
Capture the complete C4 error code and model stickers first. The source table lists the meaning but no customer reset procedure; do not treat a generic power-cycle as manufacturer guidance.
Send these to us
C4 error code, a clear display photo, Daikin indoor and outdoor model stickers, the controller, gateway, or unit that reported the code, operating mode and affected area, and any power or setting changes made after the code appeared

Source-specific guidance

These diagnostic-reference notes help match the code to the exact model. Electrical, refrigerant, wiring, resistance, and component checks are technician work, not DIY steps.

Source-specific guidance
Source detail	What it says
Singapore / model note	This row is taken from the selected Daikin operation manual's remote-controller fault diagnosis table.
Singapore / model note	Official Daikin SM-TS3 self-diagnosis row. Manual causes: Defective liquid-pipe thermistor; Defective indoor unit PCB; Defective connector contact.
Singapore / model note	Official Daikin RXQ6-48A(N)R cooling-only service-manual row. Confirm the installed model and matching regional manual before diagnosis; this source is not claimed as universal across every Daikin VRV generation.

Source detail
Singapore / model note
What it says
This row is taken from the selected Daikin operation manual's remote-controller fault diagnosis table.
Source detail
Singapore / model note
What it says
Official Daikin SM-TS3 self-diagnosis row. Manual causes: Defective liquid-pipe thermistor; Defective indoor unit PCB; Defective connector contact.
Source detail
Singapore / model note
What it says
Official Daikin RXQ6-48A(N)R cooling-only service-manual row. Confirm the installed model and matching regional manual before diagnosis; this source is not claimed as universal across every Daikin VRV generation.

What to check before repair

The source table establishes the code meaning, not a repair procedure. Capture evidence first; model-specific tests belong to the matching service manual.

Homeowner checks and technician confirmations
You can check	Technician should confirm
Photograph the complete C4 error code before taking any action.	Confirm C4 exactly and record which controller, gateway, or unit reported it.
Capture the Daikin indoor and outdoor model stickers and identify which controller or unit reported it.	Match the indoor and outdoor model stickers, installed family, and reporting equipment to the source scope.
The source table provides no customer reset procedure. Preserve the evidence and use the matching service manual for any system action.	Follow the matching service-manual procedure and keep measured test evidence before naming a failed part.

You can check
Photograph the complete C4 error code before taking any action.
Technician should confirm
Confirm C4 exactly and record which controller, gateway, or unit reported it.
You can check
Capture the Daikin indoor and outdoor model stickers and identify which controller or unit reported it.
Technician should confirm
Match the indoor and outdoor model stickers, installed family, and reporting equipment to the source scope.
You can check
The source table provides no customer reset procedure. Preserve the evidence and use the matching service manual for any system action.
Technician should confirm
Follow the matching service-manual procedure and keep measured test evidence before naming a failed part.

Source-bounded repair decision

Daikin C4 confirms the source-table fault label, not a failed part or repair procedure. Match the installed model to its service manual and require measured diagnostic evidence before approving parts, settings, or refrigerant work.

Whether the reporting controller or unit and exact installed model are confirmed.
What the matching service-manual procedure and measured tests show.
Whether the proposed repair names the evidence for the failed part or condition.

Daikin C4 questions

What does the Daikin C4 error mean?

Daikin C4 is listed as faulty heat exchanger temperature sensor, malfunction of liquid pipe thermistor for heat exchanger, and indoor heat-exchanger liquid-pipe thermistor abnormality in mixed model-family source rows, including VRV X RXQ-A(N)R cooling only, VRV 5-S RXYSA R32, VRV 5 Heat Recovery REMA / REYA R32, VRV 5 Heat Pump RYMA / RXYA R32, EKVDX / VAM R32 ventilation, Sky Air FNA R32 - indoor error overview, and EKEA / EKEXVA AHU control box. The loaded row is source-backed by official diagnostic material. Do not collapse this code across model families; use the model, series, or system type to choose the right row. Confirm the exact model, series, or signal row before accepting a parts quote.

Can I fix a Daikin C4 error myself?

No. C4 needs a technician's measurement before parts are decided. Photograph the complete C4 error code before taking any action. Capture the Daikin indoor and outdoor model stickers and identify which controller or unit reported it.

Is it safe to keep running the aircon with a C4 error?

Record C4 and stop there; the source table gives no customer reset procedure. Arrange diagnosis with the matching service manual.

What causes a Daikin C4 error?

Daikin C4 has source-backed wording that depends on the exact model, source row, or reporting unit. Use the decoder on this page before assuming a specific cause.

Will a Daikin C4 error need a repair or a full replacement?

Daikin C4 confirms the source-table fault label, not a failed part or repair procedure. Match the installed model to its service manual and require measured diagnostic evidence before approving parts, settings, or refrigerant work.

What should I send a technician about a Daikin C4 error?

Before booking, send: C4 error code, a clear display photo, Daikin indoor and outdoor model stickers, the controller, gateway, or unit that reported the code, operating mode and affected area, and any power or setting changes made after the code appeared.

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