Daikin AC Error Code F4 — What It Means & How to Fix It

What Does This Error Mean?

F4 on a Daikin AC means the outdoor heat exchanger (condenser coil) temperature thermistor has a fault. This sensor monitors the temperature of the outdoor coil during operation to regulate the refrigerant cycle. A failed or disconnected sensor triggers F4 and the system stops to protect the compressor.

Affected Models

Daikin FTKF Series
Daikin FTKG Series
Daikin ATKF Series
Daikin Inverter Split AC (all models)
Daikin 1 Ton / 1.5 Ton / 2 Ton Inverter

Common Causes

Outdoor heat exchanger thermistor failed internally
Thermistor clip dislodged from the condenser coil pipe
Thermistor wiring broken or shorted inside the outdoor unit
Connector at the outdoor PCB loose, corroded, or damaged
Outdoor PCB fault misreading a valid sensor signal

How to Fix It

Power off the AC at the remote and circuit breaker. Wait 5 minutes and restart.

If F4 clears and does not return, monitor the AC over the next few hours of use.
Note when F4 appears — immediately on startup, or after the system runs for a while.

Immediate F4 = open circuit (broken wire). F4 after running = sensor drifts out of range when heated.
If F4 persists, call Daikin service — the outdoor heat exchanger thermistor needs inspection.

The technician will check thermistor resistance and replace the sensor if it reads outside specification.

When to Call a Professional

F4 requires a Daikin authorised engineer. Do not open the outdoor unit — high-voltage components are present. Daikin India: 1800-103-3666.

Frequently Asked Questions

What does the outdoor heat exchanger thermistor do?

It clips onto the outdoor condenser coil pipe and measures refrigerant temperature as it flows through. Daikin uses this reading to control the expansion valve and protect the compressor from overheating. Without this data, the system cannot regulate refrigerant flow safely.