F2
Blue Star Split AC
Severity: ModerateWhat Does This Error Mean?
F2 on a Blue Star AC means the indoor coil (evaporator pipe) temperature thermistor has a fault. This sensor monitors the indoor heat exchanger coil temperature to prevent ice formation and regulate cooling. F2 triggers a protective shutdown to prevent the coil from freezing.
Affected Models
- Blue Star Inverter Split AC (all capacities)
- Blue Star 3 Star Inverter
- Blue Star 5 Star Inverter
- Blue Star FS Series
- Blue Star IC Series Inverter
Common Causes
- Indoor coil thermistor failed — open or short circuit
- Thermistor probe dislodged from the evaporator coil pipe
- Air filter severely blocked — coil over-cools and sensor reads at fault threshold
- Refrigerant charge incorrect — coil temperature abnormally low
- Indoor PCB fault causing incorrect coil thermistor reading
How to Fix It
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Clean the air filter — this is the first and most important step.
A heavily clogged filter severely restricts airflow over the evaporator coil, causing it to over-cool and trigger F2 protection. Clean the filter monthly.
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Switch off for 15 minutes to allow the coil to defrost, then restart.
Allow full defrost time before restarting — restarting too soon will trigger F2 again.
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If F2 clears with a clean filter, the filter was the cause.
If F2 returns despite a clean filter, the coil thermistor or refrigerant charge needs professional attention.
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Call Blue Star service (1800-209-1177) if F2 persists after filter cleaning.
The technician will test thermistor resistance and check refrigerant operating pressures.
When to Call a Professional
F2 requires a Blue Star authorised technician. Blue Star service: 1800-209-1177. If the filter cleaning does not resolve F2, the technician will test the coil thermistor and check refrigerant charge.
Frequently Asked Questions
Can I continue using Blue Star AC after F2 on cold cycles?
F2 shuts down the cooling function completely — the compressor will not run while F2 is active. Only the fan may continue to run. Do not attempt repeated restarts — resolve the root cause first.