Fujitsu AC Error Code 06 — Suction Thermistor Fault

What Does This Error Mean?

Error 06 on a Fujitsu AC means the suction thermistor — the sensor that monitors the temperature of refrigerant returning from the indoor unit back to the compressor — has a fault. This sensor is critical for protecting the compressor from liquid refrigerant slugging. The AC shuts down until the sensor issue is resolved.

Affected Models

Fujitsu ASTG Series
Fujitsu ASYG Series
Fujitsu AOTG Series
Fujitsu Inverter Split AC (all models)
Fujitsu General Split AC

Common Causes

Suction thermistor has failed — open circuit or reading out of range
Thermistor connector loose or corroded at the outdoor PCB
Thermistor probe dislodged from the suction pipe
Wiring to the thermistor damaged — chafed insulation causing a short
Outdoor PCB fault causing incorrect thermistor reading

How to Fix It

Turn off the AC and switch off the circuit breaker.

Wait 5 minutes, then restore power and attempt one restart.
If Error 06 clears after a power cycle, monitor the AC closely for the next hour.

A transient sensor fault from moisture or a voltage spike may not return. If Error 06 comes back after the unit runs for a few minutes, the thermistor has a genuine fault.
If Error 06 persists, switch off and call a Fujitsu technician.

Do not continue operating the AC without a working suction thermistor — the compressor protection that depends on this sensor will not work.

When to Call a Professional

Error 06 requires a Fujitsu authorised technician. The suction thermistor is on the refrigerant pipework and requires pressure-safe handling. A technician will test the thermistor resistance and replace it if it falls outside specification.

Frequently Asked Questions

What does the suction thermistor protect against?

The suction thermistor ensures the refrigerant returning to the compressor is fully vaporised. If liquid refrigerant reaches the compressor, it causes liquid slugging — an impact that can crack or break compressor valves. This is why a faulty suction sensor causes an immediate shutdown.

Is Error 06 common on Fujitsu ACs?

Error 06 is less common than communication or fan errors. When it does appear, it is most often due to the thermistor probe working loose from the suction pipe clip over time, especially in installations exposed to vibration.