Common problems guide

The most common Baxi Main Combi 28 problems

The faults most likely to send a Baxi Main Combi 28 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.
26 documented codes
6 most common
4 DIY-safe checks
2 engineer needed

The 6 most common faults

01
E10 High DIY-safe

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

What to try first

Locate the external filling loop, which is usually a silver flexible hose connected to the pipes underneath the boiler.Open the valves at both ends of the filling loop to allow cold mains water into the system.Watch the pressure gauge on the front of the boiler and close the valves once the needle reaches the 1.0 to 1.5 bar mark.

Est. cost
£0-£120
Parts
Filling loop, Pressure relief valve, Pressure sensor
Full guide for E10
02
Overheat indicator High DIY-safe

Your boiler has detected that it is running too hot and has automatically turned itself off to stay safe.

What to try first

Ensure your radiators are turned on and that the room thermostat is set to a demand temperature.Locate the white reset button on the boiler fascia and press it firmly.Wait a few minutes to see if the burner ignites and the light goes out.

Est. cost
£100-250
Parts
Primary overheat thermostat, Central heating pump, Diverter valve
Full guide for Overheat indicator
03
Pressure Gauge (below 0.5 bar) High DIY-safe

Your boiler has lost the water pressure it needs to circulate heat, so it has safely shut itself down to prevent damage.

What to try first

Locate the external filling loop, which is usually a flexible metal or plastic hose connected to two valves under the boiler.Open the valves slowly to allow mains cold water to enter the system until the gauge needle reaches 1.0 to 1.5 bar in the green zone.Close both valves tightly immediately to stop the flow and prevent over-pressurisation.

Est. cost
£80-150
Parts
Pressure Relief Valve (PRV), Expansion Vessel, Filling Loop
Full guide for Pressure Gauge (below 0.5 bar)
04
E119 High DIY-safe

Your boiler has stopped working because the water pressure inside the system is too low to operate safely.

What to try first

Locate the filling loop (usually a silver braided hose under the boiler).Open the valves to allow mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close both valves tightly to stop the flow of water.

Est. cost
£80-120
Parts
Pressure Relief Valve, Pressure Transducer, Expansion Vessel
Full guide for E119
05
E01 High Engineer

Your boiler is trying to start but cannot light the internal flame, which means it has stopped providing heating and hot water for safety reasons.

Est. cost
£120-250
Parts
Ignition electrode, Gas valve, Printed circuit board
Full guide for E01
06
E02 High Engineer

Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.

Est. cost
£120-250
Parts
NTC sensor, Primary heat exchanger, Pump
Full guide for E02
Parts most often replaced

on the Baxi Main Combi 28

Filling loopPressure relief valvePressure sensorPrimary overheat thermostatCentral heating pumpDiverter valve

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 Baxi 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 26-code list for the Baxi Main Combi 28

Related guides

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