Sn3
Master Spas
Auxiliary / Ambient Temperature Sensor Failure
Display shows Sn3 and spa may shut down or ignore temperature settings
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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 ambient sensor, Broken or pinched sensor wire, Loose connector on control board, Incorrect sensor type installed
How to Fix / Troubleshooting
Safety first: Turn off the spa at the GFCI breaker before inspection.
- Identify sensor: Some Master Spas models use a third sensor for ambient or cabinet temperature. It may be clipped inside the equipment bay or attached to plumbing.
- Inspect wiring: Trace the sensor cable from the sensor body to the control pack. Look for cuts, pinch points, or rodent damage. Repair or replace damaged wiring.
- Check connector: Unplug the sensor from the control board and inspect for corrosion or bent pins. Reseat firmly.
- Resistance check: With power OFF, test the sensor resistance and compare to the manufacturer’s 10k NTC chart. Replace if readings are out of range.
- Replace sensor: Install a compatible Master Spas ambient/auxiliary sensor. Route the cable away from hot components and moving parts.
- If Sn3 remains: The control pack may not be configured for this sensor or the board input may be damaged. Consult a Master Spas technician for board diagnostics or programming.
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Repair Difficulty
Medium
3/5
Required Part
Ambient / Auxiliary Temperature Sensor
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