E18
Remeha
Room thermostat / control signal fault
Boiler displays E18 and will not fire for heating
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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-circuit room thermostat wiring, Faulty on/off thermostat or OpenTherm controller, Incorrect wiring at boiler terminals, Faulty PCB input for external controls
How to Fix / Troubleshooting
Safety first: Isolate power before working on control wiring.
- Check programmer/thermostat: Ensure the room thermostat or Remeha controller is calling for heat (set temperature above room temperature, ensure timers are on).
- Bypass test (engineer): A competent person can temporarily link the boiler's room stat terminals to see if the boiler responds, confirming a control circuit issue.
- Inspect wiring: Look for loose or damaged wires at the boiler control terminals and at the thermostat.
- Engineer tasks: Test continuity of the control circuit, replace faulty thermostats or controls, and repair wiring faults.
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Repair Difficulty
Medium
3/5
Required Part
Room Thermostat / Controller
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