F1
MSPA
Primary Temperature Sensor Calibration Error
Display shows F1; spa may not heat or may behave erratically.
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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
Out-of-spec NTC sensor, Incorrect sensor installed, Corroded sensor connector, Firmware miscalibration on control PCB
How to Fix / Troubleshooting
Safety first: Disconnect power before accessing the heater or control box.
- Compare temperatures: With the spa at room temperature, compare the MSPA display reading to an external thermometer. A large difference suggests sensor calibration issues.
- Inspect sensor: Locate the primary NTC sensor on the heater tube. Check that it is firmly clamped to the metal surface and that thermal paste (if used) is intact. A loose sensor can misread.
- Check wiring and connector: Follow the sensor cable to the control PCB. Reseat the connector and inspect for corrosion or broken wires.
- Replace with correct sensor: Install a genuine MSPA NTC temperature sensor with the correct resistance curve for your model. Using a generic sensor can cause F1 errors.
- Control board replacement: If a new sensor does not resolve F1, the ADC (analog‑to‑digital converter) on the control PCB may be faulty, requiring PCB replacement.
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Repair Difficulty
Medium
3/5
Required Part
MSPA Heater NTC Temperature Sensor Assembly
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