Spa Sensors

Spa Sensors

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    Sensor, Temperature, Pentair Minimax/PowerMax

    Sensor, Temperature, Pentair Minimax/PowerMax

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    Sensor, Temperature, Pentair Minimax/PowerMax

    Pentair Pool Products

    470180
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A failed spa sensor is the single most common reason a hot tub throws an error code, locks out the heater, or refuses to maintain temperature. Our spa sensors collection covers the full diagnostic chain — temperature sensors, hi-limit (high-temperature cutoff) sensors, thermistors, mechanical thermostats, and water-level sensors — for Balboa, Sundance, United Spas, Hydro-Quip, Gecko, and Len Gordon control systems, including the M7 sensors used in modern BP-series spa packs.

If your spa is reading OH, OHH, OHS, SnA, SnB, dr, or a similar fault, replacing the temperature/hi-limit sensor pair is almost always the fix before tearing into the spa pack itself. Modern Balboa BP packs use M7 sensors — twin probes molded into a single cable with a JST connector that snaps into the pack — and these are sold in cable lengths from 12" to 96" depending on your install. Balboa's M7 tech reference explains the dual-sensor diagnostic logic. Older two-wire sensors still ship with Sundance 800, Gecko TSC, and United Spas controllers — match the connector style (box-end, curled finger, two-pin) and cable length when ordering. For the heater tube itself, see our Spa Heater Element collection.

Diagnosing a spa sensor failure is usually straightforward: pull both temp and hi-limit, measure resistance against the pack manufacturer's curve (typically around 10kΩ at 77°F for thermistor-style sensors), and replace any sensor more than 5–10% out of spec. Always replace the sensor pair together — when one fails, the other is usually close behind. For sensors that mount inside the heater housing, swap the heater gasket and o-ring at the same time; spares live in our Spa Heater Parts collection.

Shop the full spa sensor and thermistor lineup below — temp sensors, hi-limit sensors, thermistors, and thermostats all ship from one of our ten U.S. warehouses for fast turnaround on a tripping heater.

Frequently Asked Questions

How do I know if my spa temperature sensor is bad?
Most modern spa packs throw a specific error code when a sensor fails: Balboa BP packs show SnA or SnB (sensor A or B fault), older Hydro-Quip and Gecko systems show OH or HFL (high-limit), and Sundance systems often show dr or COL. Confirm with a multimeter: disconnect the sensor and read resistance at room temperature — most thermistor-style spa sensors should read around 10kΩ at 77°F. Anything more than 10% off, or readings that don't shift when you warm the probe in your hand, means replace it.
What is an M7 sensor and which spas use it?
M7 is Balboa Water Group's sensor design that combines the temperature sensor and hi-limit sensor into a single twin-probe assembly with one JST connector. All modern Balboa BP-series spa packs (BP100, BP200, BP500, BP501, BP600, BP601, BP6000, BP7) use M7. M7 sensors come in lengths from 12 inches (short pack-mount) to 96 inches (long runs to a remote heater), so measure your existing cable before ordering.
Should I replace both the temperature sensor and hi-limit sensor together?
Yes — always. The two sensors sit side-by-side in the same plumbing run and see identical thermal stress. When one fails, the other is typically 60–80% of the way to failure itself. Replacing the pair takes the same amount of work and prevents a second service call three months later. M7-style integrated sensors solve this by combining both into a single assembly, but for older two-sensor systems, never replace one in isolation.
What is the difference between a thermistor, a thermostat, and a hi-limit sensor?
A thermistor is a temperature-sensing resistor that reports continuous values to the spa pack's microprocessor — it's how the system knows the water is at 102°F vs 104°F. A thermostat is a mechanical switch that opens or closes at a fixed temperature (older Hydro-Quip and Len Gordon systems used these instead of digital control). A hi-limit sensor is a safety device that cuts heater power if the water exceeds a set ceiling (usually 119°F) — it's required by UL spa standards to prevent boil-overs.
Why does my spa keep tripping the hi-limit error even after replacing the sensor?
Hi-limit faults that persist after a sensor swap usually point to an actual high-temperature condition, not a bad sensor. Check three things: (1) low water flow — a clogged filter or air-locked plumbing causes the heater tube to overheat; (2) a stuck pressure switch keeping the heater on without flow; (3) a relay welded closed on the spa pack main board, leaving the heater energized constantly. Fix the root cause before assuming another sensor went bad.