Hot Tub Error Code Guide
SN1 / SN2 / SN3, Temperature Sensor Fault
ImportantA temperature or high-limit sensor is reading out of range (open or shorted) — usually a cheap sensor, not the heater.
Call 385-588-7757 for Fast RepairWhat Does SN1 / SN2 / SN3 Mean?
SN codes (SN1, SN2, SN3, or SNA/SNB on some systems) indicate a temperature or high-limit sensor is reading outside its expected range — open, shorted, or drifting. The control pack can't trust the reading, so it disables heating as a safety measure.
The great news for owners: sensors are inexpensive, testable parts. A good technician measures sensor resistance against the manufacturer's spec and replaces only the failed sensor, rather than swapping an entire heater assembly on a guess.
Also searched as: SN1, SN2, SN3, SNA, SNB, sensor error hot tub, high limit sensor.
Most Common Causes
- A failed or drifting temperature sensor (age, moisture intrusion, corrosion)
- A failed high-limit sensor after an overheat or scale event
- Loose, corroded, or water-damaged sensor connections at the control board
- Scale buildup affecting the sensor's contact with the water
- Occasionally, a control-board input fault rather than the sensor itself
What You Can Safely Check First
- 1
Note exactly which sensor code shows (SN1 vs. SN2 often distinguishes the temp sensor from the high-limit sensor)
- 2
Power the spa off at the breaker for a few minutes and back on to see if it was a transient fault
- 3
Visually check for obvious moisture or corrosion at the topside/board connections if the panel is easily accessible
- 4
Avoid soaking while a sensor fault is active — temperature protection is compromised
- 5
Because diagnosis requires a multimeter and spec sheet, most SN faults are best handed to a technician
Brand-Specific Notes
SN1/SN2 codes are most associated with Balboa-based systems used by Sundance and many other brands. Bullfrog and Hot Spring platforms use their own sensor sets and codes, but the diagnostic principle is identical: test resistance against spec, inspect connections, and replace only what failed.
How Urgent Is It?
A sensor fault disables heating and compromises overheat protection, so don't soak until it's resolved. It's usually a quick, inexpensive repair once the specific sensor is identified.
SN1 / SN2 / SN3 FAQs
Is an SN1 or SN2 code expensive to fix?
Usually not. Sensors themselves are inexpensive; the value is in correctly identifying which sensor failed rather than replacing the whole heater. We test resistance against spec and replace only the failed part.
Can I use my hot tub with a sensor error?
Better not to. The sensor provides temperature and overheat protection, so heating is disabled and safety is reduced. Have it diagnosed before soaking again.
Still Seeing SN1 / SN2 / SN3?
Send us your spa brand and the code, we'll diagnose the root cause and bring the right parts.
Other Hot Tub Error Codes
SN1 / SN2 / SN3 on your display? Let's fix it right.
Owner-operated, CPO Certified repair across the Heber Valley, Summit County, and Utah County. We diagnose the root cause, not just reset the code.