SN1
Hot Spring
Water Temperature Sensor Failure
Display shows “SN1”; spa may not heat or may behave erratically with temperature.
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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 water temperature thermistor, Corroded sensor connector, Broken sensor lead, Control board sensor input fault
How to Fix / Troubleshooting
Safety first: Shut off power at the GFCI breaker.
- Locate the water temperature sensor: On most Hot Spring models, this thermistor is threaded into the heater housing or nearby plumbing.
- Inspect and reseat: Disconnect the sensor plug from the IQ control board, inspect for corrosion, clean gently if needed, and reconnect firmly.
- Replace sensor if needed: If SN1 remains, unscrew the old thermistor from the heater, install a new OEM Hot Spring thermistor with the supplied O-ring or sealant, and reconnect the wiring.
If a new sensor does not resolve SN1, the control board’s sensor circuit may be defective and require professional replacement.
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Repair Difficulty
Medium
3/5
Required Part
Water Temperature Thermistor
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