F5
Panasonic Split AC
Severity: ModerateWhat Does This Error Mean?
F5 on a Panasonic AC means the discharge pipe thermistor — the sensor that monitors the temperature of hot refrigerant gas leaving the compressor — has a fault. This is a critical safety sensor. The AC shuts down to protect the compressor until the sensor is fixed.
Affected Models
- Panasonic CS-RU Series
- Panasonic CS-PU Series
- Panasonic CS-XU Series
- Panasonic Inverter Split AC (all models)
- Panasonic NanoeX Series
Common Causes
- Discharge pipe thermistor has failed — resistance value out of spec
- Thermistor probe has come loose from the discharge pipe clamp
- Connector corroded or pulled out at the outdoor PCB
- Thermistor wiring damaged inside the outdoor unit casing
- Outdoor PCB misreading the thermistor signal
How to Fix It
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Turn off the AC and circuit breaker.
Wait 5 minutes, restore power, and attempt one restart. If F5 appeared after a power event, a power cycle may clear it.
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Note whether F5 appears immediately or after the AC has been running for some time.
Immediate F5 on startup suggests an open-circuit thermistor (broken wire or failed sensor). F5 that appears after 10–20 minutes of running suggests the sensor drifts out of range as it warms up.
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If F5 persists, call a Panasonic authorised technician.
Do not continue restarting — the discharge thermistor is a compressor protection sensor. Operating the compressor without it risks overheating and permanent compressor damage.
When to Call a Professional
F5 requires a licensed HVAC technician. The discharge pipe thermistor is located in the outdoor unit near the compressor — an area with high-voltage components and pressurised refrigerant lines.
Frequently Asked Questions
What does the discharge pipe thermistor protect on a Panasonic AC?
The discharge thermistor monitors the temperature of compressed hot refrigerant gas leaving the compressor. If this temperature gets too high — indicating the compressor is working too hard, the refrigerant level is low, or the condenser is blocked — the inverter board reduces compressor speed or shuts down. Without this sensor, the compressor has no protection against overheating.
Is F5 an expensive repair on a Panasonic AC?
The thermistor part itself is inexpensive — typically $10–30. The majority of the repair cost is the technician's visit and labour. For a unit still under warranty, a thermistor failure is a covered repair.