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Sn1 on a Jacuzzi / Sundance hot tub: hi-limit sensor fault

The high-limit sensor is open or shorted, and the heater is turned off. The tub will not heat until the sensor is replaced.

Also shown as: SN1, Sn 1

Most likely causes

  1. 1Failed hi-limit sensormost likely
  2. 2Loose or corroded connectorcommon
  3. 3Damaged sensor cablecommon
  4. 4Circuit board faultless common

What to try, in order

  1. Reset power at the breaker for 30 seconds.
  2. With power off, look for damaged wiring in the equipment bay.
  3. Have your model and serial number ready, since sensors differ by model year.
  4. Contact your dealer or a technician for a sensor replacement.

Sn1 questions

What does Sn1 mean on a Jacuzzi or Sundance?

It means the high-limit sensor has failed or lost its connection. The heater is disabled as a precaution.

Can I keep the tub running?

The pumps may still work, but there is no heat. In freezing weather, get it repaired promptly.

Related codes

Hydro-Quip Sn1 · Hi-limit sensor faultJacuzzi / Sundance -- · Watchdog shutdownJacuzzi / Sundance COOL · Water 20°F below setJacuzzi / Sundance FL1 · No flow detectedJacuzzi / Sundance FL2 · Flow switch stuck closedJacuzzi / Sundance FLO · Flow switch problemJacuzzi / Sundance HOLD · Panel buttons locked outJacuzzi / Sundance ICE · Freeze protection active

General guidance. Follow your manufacturer's instructions; anything inside the control box is work for a licensed professional. Updated October 5, 2026.