Mistral Condensing Boiler Error Codes

Mistral Condensing Boiler Error Codes

Mistral Error Codes

The Mistral Condensing boiler range is normally extremely reliable and powerful.

Occasionally some things can go wrong, that’s why we’ve created our handy at-a-glance table of Mistral error codes below.

Should you need professional help with your broken boiler, then simply use our enquiry forms, and we will connect you with the best heating engineers local to you.

Need a boiler repair?



Initial user checks

You are able to make some checks before calling out a service engineer.

  • Check you have enough fuel: check the sight gauge.
  • Check the fuel supply valves are open.
  • Check the external fire valve hasn’t tripped: press the trip button.
  • Is the boiler electrical supply on?
  • Is the control panel high limit thermostat tripped? Check and reset if needed.
  • Burner control box locked out: check and press the lens.

Mistral Boiler Error Codes

Fault Possible Cause
Burner does not start / run Air locks/ Supply lines blocked or tank vent blocked (no fuel getting into tank)
Restriction suspected / fuel supply fault Power supply to the boiler failed/ Burner control box locked out/ Burner motor fault/ Pump seized
Burner fault locks out after 15 seconds Photocell fault/ Restricted oil supply/ Combustion setting out of specification
No flame established (burner fault) Ignition failure/ Oil restrictor/ Nozzle locked
Burner fault runs but continually pulsates Condensate trap blocked/ flue system blocked/ Baffles wrongly positioned on boiler
Lock-out Losing oil in the supply suction line/ Oil level in tank below minimum level
Burner running but smokes Tank topped with wrong fuel/ Air supply restricted/ Dust build up
Burner flame shuts down slowly Balanced flue system leaking/ Combustion leaks/ Suction line drawing air into fuel
Burner fails to reach working temperature Burner output restricted/ Low efficiency/ Control thermostat fault
Oil smells Oil leakage at connection
No hot water Circulating pump seized/ Programmer channel off
Flow and water temperature low Programmer for CH or DHW are off/ Debris build-up/ Low water supply pressure
CH and or DHW not working Programmer channels are off/ Thermostats fault or turned off
Thermostat trips off Fault circulating pump
No CH Spring fault or return valve not moving or operating properly/ Room stat error
No DHW Spring fault/ Jammed in HW mode/ Flow switch blocked or faulty
Discharges on pressure relief valve Pressure vessel has lost charge/ Insufficient expansion volume

Need a boiler repair?



  • View the Boiler Guide home of Mistral
  • See the common problems and get repair advice for your Mistral boiler