E04
Rocket Espresso
Boiler Temperature Sensor / Probe Fault
PID or digital display shows a sensor error, temperature reading is erratic, stuck at one value, or shows dashes instead of a number.
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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 NTC temperature probe, Broken or shorted sensor wiring, Loose connector at PID controller or Gicar box, Corroded probe threads causing poor contact
How to Fix / Troubleshooting
Safety first: Unplug the machine and let it cool completely before accessing the boiler area.
- Power cycle the machine: Turn the machine OFF, wait 30 seconds, and turn it back ON. If the error clears temporarily but returns, the sensor or wiring is likely intermittent.
- Inspect sensor wiring: Remove the top cover and trace the thin sensor wires from the boiler probe to the PID or control box. Look for pinched, cut, or melted insulation. Reseat any plug-in connectors.
- Check for corrosion: At the boiler, inspect the probe base for leaks or heavy scale. Minor scale can be gently cleaned; if the probe is seized or leaking, replacement is recommended.
- Do not operate with a known sensor fault: The machine may overheat or underheat without accurate temperature feedback. If wiring appears intact, replace the NTC probe with a Rocket-compatible part.
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Repair Difficulty
Medium
3/5
Required Part
Boiler NTC Temperature Probe
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