E04
NetSpa Temperature Sensor (NTC) Fault

Display shows E04 and heating is disabled; spa may still circulate water.

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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

Open or shorted NTC temperature probe, Damaged sensor wiring harness, Corroded connector at control PCB, Faulty main control PCB input circuit

How to Fix / Troubleshooting

Safety first: Disconnect power before opening the NetSpa motor/heater unit.

  • Power cycle: Unplug the spa for 5 minutes, then reconnect and check if E04 clears. Temporary glitches can sometimes be reset.
  • Inspect sensor cable: Locate the temperature sensor cable entering the heater tube or control box. Check for cuts, pinches, or rodent damage along the cable.
  • Check connectors: If accessible, gently unplug and replug the sensor connector on the control PCB to clear oxidation. Do not force or bend pins.

If the error remains, the NTC temperature sensor or the control PCB is likely defective. Replacing the NetSpa temperature sensor probe is usually the first step; if that does not resolve the issue, the main control unit may need replacement by a professional.

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Repair Difficulty

Hard 4/5

Required Part

NetSpa NTC temperature sensor probe
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