Hot tub Sn and temperature sensor codes
Short answer
Sn codes are temperature sensor faults. SnS (or Sn) means the heater's two sensors disagree by 2°F or more; SN1, SN2, SA and Sb mean one sensor has failed or its circuit is open or shorted. An owner cannot fix a sensor: check for overheating, then call a technician.
What you can check yourself
- Stay out of the water.
- Turn the power off at the breaker for 30 seconds, then back on. Once.
Where the owner's part ends
Anything else: turn off power at the breaker and call a technician.
Sensors sit in the heater and plug into the control board. Testing, swapping or replacing them is a technician's job. Never unplug, bypass or jumper a temperature sensor.
Every sensor code, system by system
20 codes
| Code | What it means | What to do |
|---|---|---|
| M015Balboa, M codes | Panel: Sensors are out of syncThe two temperature sensors in the heater may disagree by 2 to 3°F. Balboa says to call for service. | Technician Call for service if it does not clear within a few minutes. |
| M026Balboa, M codes | Panel: Sensors are out of sync, call for serviceThe heater's two sensors have disagreed for at least an hour. | Technician Call for service. |
| M031Balboa, M codes | Panel: Sensor A faultTemperature sensor A or its circuit has failed. | Technician Call for service. |
| M032Balboa, M codes | Panel: Sensor B faultTemperature sensor B or its circuit has failed. | Technician Call for service. |
| SnSAlso: Sn, SENSOR SYNCBalboa panel letters | Panel: Sensors out of syncThe two heater sensors read 2°F or more apart when not heating. Balboa's service manual notes the same reading can also trigger the flow messages. | Technician Call for service. |
| E5Hot Spring 2026 | Panel: E5: SENSOR FAULTA control sensor fault; the heater is off. The status ring flashes red. | Technician Call for service. |
| READY icon flashingHot Spring Hot Spot | Panel: READY flashingThe control sensor is open or shorted. | Technician Contact an authorized service technician. |
| Orange logo light blinkingCaldera 2026 | Panel: Ready indicator blinkingA temperature sensor problem. | Check first
Call if blinking continues after one power reset. |
| SN--1Jacuzzi 2017 | Panel: HI-LIMIT SENSOR ERRORThe high-limit sensor is open (heater off) or shorted (spa off). | Technician Contact your Jacuzzi dealer. |
| SN--2Jacuzzi 2017 | Panel: WATER SENSOR ERRORThe water temperature sensor is open or shorted; the heater is off. | Technician Contact your Jacuzzi dealer. |
| Code 15Jacuzzi 2025 on | Panel: Sensor Balance TransientTemperature sensors out of sync; the heater is off. | Check first
Contact your dealer if it persists after one power reset. |
| Code 26Jacuzzi 2025 on | Panel: Sensor Balance LatchSensor error; the heater is off. | Check first
Contact your dealer if it continues. |
| Code 31 / 32Jacuzzi 2025 on | Panel: Sensor Fault A / BA heater sensor fault. | Technician Contact your dealer. |
| SN1Sundance 2016 | The high-limit sensor is open (heater off) or shorted (spa off). | Technician Your Sundance dealer must repair it. |
| SN2Sundance 2016 | The water temperature sensor is open or shorted; the heater is off. | Technician Your Sundance dealer must repair it. |
| Code 15Sundance 880, 2025 | Panel: Sensor Balance TransientThe temperature sensors are out of sync. | Technician Call if it does not clear. |
| Code 26Sundance 880, 2025 | Panel: Sensor Balance LatchThe sensors are out of sync. | Technician Contact your dealer or service company. |
| Code 31 / 32Sundance 880, 2025 | Panel: Sensor Fault A / BSensor A or sensor B has a fault. | Technician Contact your dealer or service company. |
| SA, SbAlso: SnT, SnH, SNSR A, SNSR BVita Spa 2026 | Panel: Sensor A fault, Sensor B faultHeater sensor A or B is not working; the spa shuts itself off. | Technician Contact your dealer for a replacement sensor. |
| SnSAlso: Sn, SNSR SYNCVita Spa 2026 | Panel: Sensors are out of syncThe heater sensors are out of balance; the spa shuts itself off. | Technician Contact your dealer. |
Why does a hot tub have two temperature sensors?
One keeps the temperature, the other guards against overheating, and comparing them tells the control about flow. Jacuzzi's 2017 J-300 labels them plainly: SN--1 is the high-limit sensor, SN--2 the water sensor. Balboa's M7 heaters put one at each end of the element; with no water flowing, the two readings drift apart, so the same gap that sets off SnS can also set off the low-flow messages.
What should I do about a sensor code?
Rule out heat first. Balboa says its Sensor A and B messages can appear briefly during an overheat. If the water is normal, try one power reset where the manual allows it, and if the code stays, it is a service call.
A temperature sensor problem was behind a CPSC recall of some Jacuzzi and Sundance hot tubs. See hot tub recalls to check yours.
Common questions
What does SnS mean on a hot tub?
Sensors out of sync: the two temperature sensors in the heater read too far apart. Balboa treats a 2°F gap when not heating as excessive. If the panel shows it alone and flashing, the spa has shut down.
What is the difference between SN1 and SN2?
On the 2017 Jacuzzi J-300 and 2016 Sundance 680, SN1 is the high-limit sensor and SN2 the water temperature sensor. Both need a dealer repair.
Can I reset a hot tub sensor error?
Jacuzzi's J5 manual says to reset the power once for codes 15 and 26. If the code returns, the sensor or its wiring needs a technician. Never unplug or bypass a sensor.
Can an overheated tub show a sensor code?
Yes. Balboa notes that its Sensor A and Sensor B messages may appear for a while during an overheat. Check the water temperature and let it cool before you assume a sensor failed.
Sources
11
- Balboa TP400/TP600 user guide (40940_N), panel messages
- Balboa troubleshooting and service manual for EL/VS systems
- Hot Spring Highlife Collection owner's manual, 2026
- Hot Spring Hot Spot Collection owner's manual, 2026
- Caldera Spas Utopia Series owner's manual, 2026
- Jacuzzi J-300 owner's manual, 2017
- Jacuzzi J5 owner's manual (rev A)
- Sundance Spas 680 Series owner's manual, 2016
- Sundance Spas 880 Series owner's manual, 2025 (rev E)
- Vita Spa owner's manual, 2026
- Balboa VL401 user guide (40789_G), diagnostic messages
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