SE
Bullfrog Spas General Sensor Error or Sensor Out of Range

Display shows SE or SENSOR; spa may shut down heating and pumps

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Shorted or open temperature sensor, Damaged sensor harness, Moisture in sensor connector, Control board sensor circuit failure

How to Fix / Troubleshooting

Safety: Turn OFF power at the GFCI breaker before inspecting sensors or wiring.

  • Inspect sensor wiring: Open the equipment bay and locate the M7 sensors on the heater tube. Follow their cables to the control board. Look for cuts, abrasions, or melted insulation.
  • Check connectors: Unplug each sensor connector from the control board, inspect for corrosion or moisture, dry if necessary, and reconnect firmly.
  • Measure resistance: With power OFF, use a multimeter to measure resistance of each sensor. Compare readings to each other and to a temperature/resistance chart if available. Replace any sensor that is open, shorted, or far out of range.
  • Replace sensor pair if needed: For reliability, replace both M7 sensors as a matched pair if one has failed.
  • Reset and test: Restore power and verify that SE clears and the spa operates normally.

If SE persists with new sensors and good wiring, the control pack likely has an internal fault; replacement of the control board or entire pack may be required.

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Repair Difficulty

Hard 4/5

Required Part

M7 Temperature Sensor Kit or Main Control Board
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