Jacuzzi pool heater display shows LO and the heater will not fire.

Safety first: Turn off power before accessing the sensor.

Steps to address LO:

• Verify actual water temperature: Use a separate pool thermometer to confirm the real water temperature. If the pool is not extremely cold but LO is displayed, suspect the sensor.
• Inspect sensor placement: Ensure the Jacuzzi water temperature sensor is fully seated in the manifold well and secured with its clip or fitting.
• Check wiring: Inspect the sensor cable for cuts, abrasions, or rodent damage. Confirm the connector is clean and firmly attached to the control board.
• Test and replace sensor: Measure sensor resistance and compare to Jacuzzi’s chart. Replace the sensor if readings are out of range.

If LO persists with a known-good sensor, the control board may require professional diagnosis and replacement.