Jacuzzi / Sundance · Jacuzzi J-300 / J-400 and later Sundance seriesFix soon

FL2 on a Jacuzzi / Sundance hot tub: flow switch stuck closed

The flow switch reads closed when the pump is off, which means the switch is stuck or has failed. The heater is locked out until it is fixed.

Also shown as: FL 2, FLO2

Most likely causes

  1. 1Flow switch stuck closed by debris or scalemost likely
  2. 2Failed flow switchcommon
  3. 3Wiring or circuit board faultless common

What to try, in order

  1. Reset power at the breaker for 30 seconds.
  2. Test and correct calcium hardness and pH, since scale can jam the switch.
  3. If the code returns, have the flow switch replaced.

FL2 questions

Will cleaning the filter fix FL2?

Not usually. FL2 points at the switch itself, not at low flow.

Can I still use the tub?

You can soak, but the heater will not run, so the water will cool.

Related codes

Jacuzzi / Sundance -- · Watchdog shutdownJacuzzi / Sundance COOL · Water 20°F below setJacuzzi / Sundance FL1 · No flow detectedJacuzzi / Sundance FLO · Flow switch problemJacuzzi / Sundance HOLD · Panel buttons locked outJacuzzi / Sundance ICE · Freeze protection activeJacuzzi / Sundance OH · Overheat protectionJacuzzi / Sundance Sn1 · Hi-limit sensor fault

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