Common problems guide

The most common Sime Murelle EV HE Combi problems

The faults most likely to send a Sime Murelle EV HE Combi into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.
23 documented codes
6 most common
2 DIY-safe checks
4 engineer needed

The 6 most common faults

01
02 High DIY-safe

Your boiler has stopped working because the water pressure inside the heating system has dropped too low.

What to try first

Locate the filling loop, which is a silver braided hose or a small valve under the boiler.Open the valve(s) slowly to allow cold mains water into the system until the pressure gauge reads between 1 and 1.5 bar.Close the valve(s) tightly and check that the error code has cleared.

Est. cost
£0-£100
Parts
Filling loop, Pressure relief valve, Pressure gauge
Full guide for 02
02
07 High DIY-safe

Your boiler has detected that the water pressure inside the system is too low, preventing it from heating your home or water properly.

What to try first

Locate the external filling loop (usually two silver flexible braided hoses underneath the boiler).Slowly open the valves on the filling loop to allow cold mains water to enter the system.Monitor the pressure gauge on the front of the boiler until the needle reaches the green zone (typically 1.0 to 1.5 bar).Close both valves tightly to prevent over-pressurisation.

Est. cost
£0-£100
Parts
Filling loop, Pressure relief valve, Pressure transducer/sensor
Full guide for 07
03
01 High Engineer

Your boiler has detected that it is overheating and has automatically switched itself off to prevent damage.

Est. cost
£120-250
Parts
Safety thermostat, Central heating pump, Diverter valve
Full guide for 01
04
04 High Engineer

Your boiler has lost the ability to monitor the temperature of your hot water supply, meaning it will likely stop producing hot water until the faulty sensor is replaced.

Est. cost
£120-200
Parts
DHW NTC Sensor
Full guide for 04
05
05 High Engineer

Your boiler has stopped working because it is unable to accurately measure the temperature of the water used for your heating system.

Est. cost
£120-220
Parts
Central heating NTC thermistor, Wiring harness
Full guide for 05
06
06 High Engineer

Your boiler has detected a serious internal fault and has automatically shut itself down for safety reasons, meaning you currently have no heating or hot water.

Est. cost
£150-300
Parts
Control board, Ignition transformer, Flame sensor
Full guide for 06
Parts most often replaced

on the Sime Murelle EV HE Combi

Filling loopPressure relief valvePressure gaugePressure transducer/sensorSafety thermostatCentral heating pump

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Sime shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
See the full 23-code list for the Sime Murelle EV HE Combi

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →