F4
Tempstar
Outdoor Discharge Temperature Sensor Fault
Tempstar ductless mini-split indoor unit displays F4 and no cooling occurs
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Failed compressor discharge thermistor, Sensor dislodged from discharge line, Damaged sensor wiring, Faulty outdoor control board
How to Fix / Troubleshooting
Safety first: Turn OFF power at the outdoor disconnect. The discharge line can be extremely hot during operation.
Steps:
- 1. Access compressor compartment: Remove the outdoor unit panel to locate the discharge line sensor near the compressor outlet.
- 2. Verify sensor placement: Ensure the thermistor is securely attached to the discharge line with a clip or strap.
- 3. Inspect wiring: Look for insulation damage or loose connectors.
- 4. Reseat connector: Disconnect and reconnect the sensor plug on the control board.
- 5. If F4 remains: The sensor or board is likely defective and should be replaced by a qualified technician.
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Repair Difficulty
Hard
4/5
Required Part
Discharge Line Thermistor
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