F2
MSPA
Secondary / Backup Temperature Sensor Fault
MSPA spa shows F2; heating may be disabled and temperature readings fluctuate wildly.
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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 backup NTC sensor, Shorted sensor wiring, Moisture in sensor connector, Damaged control PCB sensor input
How to Fix / Troubleshooting
Safety first: Unplug the spa and ensure the area around the control unit is dry.
- Locate backup sensor: Some MSPA models use a second NTC sensor on the return line or inside the heater housing. Identify this sensor using the service manual or wiring diagram.
- Inspect for moisture: Check the sensor connector and surrounding area for condensation or leaks. Dry thoroughly and correct any water ingress sources (loose hose clamps, perished O‑rings).
- Check cable integrity: Look for crushed, cut, or abraded sensor cables. Replace the MSPA backup NTC sensor if any damage is found.
- Test resistance: With a multimeter, measure the sensor resistance at room temperature and compare to the primary sensor. Large discrepancies indicate a faulty sensor.
- Replace control PCB if needed: If both sensors test correctly but F2 persists, the sensor input circuit on the PCB may be defective.
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Repair Difficulty
Medium
3/5
Required Part
MSPA Backup NTC Temperature Sensor
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