E18
Main
Water Pressure Sensor Range/Calibration Fault
Boiler shows E18, pressure gauge may read very high or very low
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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
Defective pressure sensor, Blocked sensor connection, Air trapped at sensor, PCB misreading sensor
How to Fix / Troubleshooting
Safety: Do not operate the boiler if the pressure is above the red zone. Allow the system to cool before draining or venting.
- Compare gauge and display: If the digital pressure reading on the Main display does not match the mechanical gauge, the sensor may be faulty.
- Normalise pressure: If pressure is too high (>2.5 bar), bleed a radiator to reduce it. If too low, top up via the filling loop.
- Engineer tasks:
- Remove and inspect the pressure sensor connection for blockage or air lock.
- Replace the Main water pressure sensor if readings remain erratic.
- Check the PCB analogue input circuit for correct operation.
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Repair Difficulty
Medium
3/5
Required Part
Water Pressure Sensor
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