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Bullfrog Spas Temperature Not Available / Sensor Not Reading

Display shows two dashes or blank temperature; spa may not heat

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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

Disconnected temperature sensor, Spa in priming mode, Sensor failure, Control board not receiving sensor data

How to Fix / Troubleshooting

Safety: Turn OFF power at the GFCI breaker before inspecting internal components.

  • Wait for priming to finish: After power-up, the spa may show dashes while in priming mode. Follow the manual to exit priming and allow the spa to start normal operation.
  • Inspect sensor connections: Open the equipment bay and verify that both M7 sensor plugs are firmly seated on the control board.
  • Check sensor resistance: With power OFF, measure resistance of each sensor. Replace any that are open or shorted.
  • Power cycle: Restore power and confirm that the temperature now displays correctly.

If the display remains as dashes with good sensors, the control board may be defective.

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Repair Difficulty

Medium 3/5

Required Part

M7 Temperature Sensor or Control Board
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