4
Senseo
Thermistor / Temperature Sensor Fault
Error 4 or four flashing LEDs; machine does not heat, coffee is cold or brewing does not start.
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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 boiler thermistor, loose thermistor wiring connector, damaged harness between thermistor and control PCB, overheated boiler causing sensor failure
How to Fix / Troubleshooting
Safety first: Unplug the machine and let it cool for at least 30 minutes. The boiler and metal parts can be very hot.
- Power reset: After cooling, plug the unit back in and try again. Temporary overheat can trigger a sensor error.
- Check for descaling need: Heavy scale can cause localized overheating. Run a full descaling cycle if the machine will allow it.
- Inspect wiring (advanced): Remove the top cover and visually inspect the small sensor clipped to the boiler (usually two wires). Look for burnt insulation, broken wires, or loose connectors.
- Do not bypass sensor: Never short or bypass the thermistor; this is a critical safety device.
- Professional service: If the thermistor or wiring is damaged, have a technician replace the thermistor and check the boiler for damage.
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Repair Difficulty
Professional Required
5/5
Required Part
Boiler Thermistor (Temperature Sensor)
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