Hot tub showing a sensor error?
Sn1, Sn3 and SN codes flag a temperature or hi-limit sensor fault — usually a failed sensor or corrosion at its connection, and occasionally a board issue. The sensor is part of the heater assembly, so it's an affordable, fast fix.
from $149 · $69 diagnostic credited to your repair
The board has lost faith in its thermometer
Sn1, Sn2, Sn3 and SN are sensor faults. Your spa relies on small thermistor sensors — typically a temperature sensor and a high-limit sensor mounted in or near the heater — to know how hot the water is. When the board reads a value that's impossible, out of range, or wildly inconsistent between the two, it can't trust the reading, so it throws a sensor code and shuts the heater down rather than guess.
The most common cause is simply a sensor that has failed. These thermistors drift and die with age and heat cycling, and once one reads open or shorted, the code latches. Close behind is corrosion or a loose connection at the sensor plug — South Florida's humidity and spa chemistry work on those contacts over time, and a poor connection looks identical to a dead sensor from the board's point of view.
Occasionally the sensor is fine and the fault is on the control board itself — a bad input channel reading the sensor wrong. That's the less common case, which is exactly why testing matters: we read each sensor against spec before condemning a board. Because the temperature and hi-limit sensors are integral to the heater assembly, replacing them is a quick, affordable repair when they're the cause.
Test the sensors against spec, then replace the fault
Test
We measure each sensor's resistance against spec and inspect the connections for corrosion before condemning anything.
Flat quote
Once we know it's the sensor, the connection or the board, you get the published price up front — diagnostic credited.
Replace
We fit the correct temperature or hi-limit sensor for your heater assembly, clean and re-seat the connections, or address the board.
Verify
We confirm the panel reads the true water temperature and the heater holds its set-point before we leave.
Most sensor-error repairs are completed same-day across Palm Beach County.
A sensor code is worth confirming before you buy a board
It's tempting to assume a sensor fault means a new control board, but more often it's the inexpensive sensor or a corroded plug. We test the thermistors directly so you don't pay for a board you didn't need — and if the board really is the issue, we'll tell you plainly.
Flat-rate, published up front
A sensor replacement is the same flat rate as a flow switch; a full heater assembly applies only if the sensor isn't serviceable separately — confirmed at your $69 diagnostic.
Not quite your symptom?
Overheating (OH)
A sensor reading high can trip a false overheat shutdown.
HeaterWon't heat at all
A misreading sensor can stop the heater from firing.
HeaterHeater not working
The element, high-limit or sensor in the heating chain.
HeaterElement replacement
When the element, not the sensor, is the failed part.
Answers before you call
They're sensor faults. The board read an out-of-range or inconsistent value from a temperature or high-limit sensor and shut the heater down rather than trust a bad reading. The usual cause is a failed sensor or a corroded connection.
Not usually. Far more often it's the inexpensive sensor itself or a corroded plug. We test the thermistors against spec before condemning a board, so you don't pay for a board you didn't need.
No — with a faulty sensor the board can't reliably know the water temperature, which is a safety concern. Leave the heater off until the sensor is tested and replaced.
From $149 for a sensor or hi-limit replacement. A full heater assembly only applies if the sensor isn't serviceable on its own. You get the flat price before we start.
Same-day across most of Palm Beach County, with a real arrival window rather than a vague all-day wait.
We'll test the sensor — not guess at a board.
Flat-rate from $149. Same-day. $69 diagnostic credited to your repair.
Tell us the code on the panel — we'll call back within the hour
No call center. Just a local, licensed tech who'll test the sensors and quote the price before any work.
Quote request sent
We'll call you back within the hour. Hot tub out cold right now? Call us at (561) 555-0143.