H8
AstralPool Outlet Temperature Sensor / Differential Fault

Heater shows H8; temperature reading on display is obviously wrong (e.g., 0°C or 99°C constantly).

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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

Failed outlet temperature sensor, Loose sensor in well causing poor contact, Wiring harness fault, Control board sensor circuit failure

How to Fix / Troubleshooting

Safety first: Disconnect power before removing panels.

  • Compare displayed temperature: Compare the heater’s displayed water temperature to an external pool thermometer. Large discrepancies suggest a sensor issue.
  • Inspect outlet sensor: Locate the outlet sensor on the heater’s water outlet manifold. Ensure it is fully inserted into its well or securely clamped to the pipe.
  • Check wiring: Follow the sensor cable back to the control board, checking for damage or loose connectors.
  • Reset heater: After reseating connectors, restore power and see if the error clears.

If H8 remains, the outlet sensor should be replaced. If a new sensor does not resolve it, the main control board may require replacement.

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Repair Difficulty

Medium 3/5

Required Part

AstralPool Outlet Temperature Sensor
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