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SN4

Sundance Hot Tub

Severity: Moderate

Source: OnlyErrorCodes.com — Every error code. One place.

Sundance Spa SN4 Error — Heater High-Limit Sensor Fault

What Does This Error Mean?

Sundance SN4 means the high-limit temperature sensor is open or shorted.
The control board reads no valid signal from the safety sensor that protects against overheating.
Sensor often fails from age, water exposure to the connector, or scale buildup.
Replacement sensor is 30-60 USD; the job takes about an hour with the spa power off.

Affected Models

  • Sundance Cameo
  • Sundance Optima
  • Sundance Maxxus
  • Sundance Aspen
  • Sundance Capri

Common Causes

  • High-limit sensor failed (open circuit)
  • Wire harness damaged or chewed by rodents
  • Connector corroded by water seepage
  • Scale insulating the sensor from the heater pipe
  • Control board sensor input fault (rare)

How to Fix It

  1. Power off at the breaker.

    Hot tubs run 240V.
    Switch off and use a non-contact voltage tester near the heater terminals to confirm power is off.

  2. Locate the high-limit sensor.

    Open the equipment access panel.
    The high-limit sensor is a small probe clamped to the heater pipe — usually a metal tab or strap holds it against the stainless steel surface.
    It connects to the board with a 2-wire cable.

  3. Inspect the sensor and wires.

    Look for cracked insulation, green corrosion at the connector, or rodent damage.
    If the connector is corroded, remove and clean with electrical contact cleaner; reseat firmly.

  4. Test the sensor (optional).

    Disconnect the sensor at the board.
    Use a multimeter on ohms.
    At room temperature, the sensor should read about 8-12k ohms (Sundance uses NTC thermistors).
    OL = open = bad.
    Very low ohms = shorted = bad.

  5. Replace the sensor.

    Match the part number on the existing sensor (or look up by spa model).
    Mount the new sensor against bare metal — scale or paint between sensor and pipe blocks heat transfer.
    Plug into the same connector.
    Power on and confirm SN4 clears.

Frequently Asked Questions

How does this sensor differ from the regular temperature sensor?

Sundance uses two sensors: one reads water temperature for normal operation, one is a safety high-limit that shuts the heater off if temperature exceeds 119°F.
SN4 is the high-limit; SN1 or SN2 codes (depending on board) are the operating sensor.
Don't swap them — the high-limit has a different calibration.