SN
Hot Spring
Sensor Fault (Temperature or High-Limit Thermistor)
Display shows “SN”, “SN1”, or “SN2”; spa may not heat or may shut down.
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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
Open or shorted temperature sensor, Open or shorted high-limit sensor, Loose sensor connector at control board, Damaged sensor cable
How to Fix / Troubleshooting
Safety first: Turn off power at the breaker before touching any wiring.
- Identify which sensor: On many Hot Spring models, SN1 refers to the water temperature sensor and SN2 to the high-limit sensor. A generic “SN” may indicate either.
- Inspect sensor connections: Open the equipment compartment and locate the thermistor leads going to the IQ control box. Unplug and replug each connector to ensure a solid connection.
- Check for cable damage: Follow the sensor wires from the heater or plumbing to the control box. Look for cuts, rodent damage, or pinched sections.
- Replace faulty sensor: If the error persists, replace the suspect temperature sensor (thermistor) or high-limit sensor. These typically thread into the heater manifold and can be swapped with basic tools.
If replacing sensors does not clear the error, the control board may have a sensor circuit fault and should be evaluated by a technician.
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Repair Difficulty
Medium
3/5
Required Part
Temperature Sensor (Thermistor)
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