Main Eco 24 HE Fault codes & diagnostics

8 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 24 kW 2006-2010 Discontinued

Replaced by: Main Eco Elite

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Severity at a glance

Each cell = one fault code. Hover to identify.
8 High

All 8 documented codes

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E20

Your boiler has lost the ability to accurately measure the temperature of the radiator water, so it has shut down to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • Central Heating NTC Sensor
  • Wiring Harness

Related codes

E28

Your boiler's computer module has been identified as incompatible or was recently replaced incorrectly, preventing the system from operating safely.

High Engineer only £250-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
E50

Your boiler is struggling to accurately measure the temperature of the water being heated for your taps, so it has stopped providing hot water to ensure your safety.

High Engineer only £120-220

Parts commonly replaced

  • Domestic Hot Water (DHW) NTC Thermistor

Related codes

E110

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

High Engineer only £120-250

Parts commonly replaced

  • Overheat Thermostat
  • Central Heating Pump
  • Diverter Valve
  • System Filter

Related codes

E119

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

High DIY-safe £80-150

What to check first

  1. Locate the external filling loop, usually a silver braided hose near the boiler
  2. Slowly open the valves on the loop to allow mains water into the heating system
  3. Watch the pressure gauge on the front of the boiler until the needle reaches between 1.0 and 1.5 bar
  4. Close both valves tightly and remove the filling loop if required

Parts commonly replaced

  • Pressure relief valve
  • Pressure transducer
  • Filling loop
E125

Your boiler has detected that hot water is not circulating properly around your heating system, so it has shut down to prevent overheating.

High Engineer only £150-350

Parts commonly replaced

  • Pump
  • Diverter Valve
  • System Filter

Related codes

E133

Your boiler has stopped working because it cannot detect a flame, which is often caused by a lack of gas supply or a temporary ignition glitch.

High Engineer only £120-250

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • PCB

Related codes

E160

Your boiler has stopped working because the mechanical fan responsible for pushing out exhaust gases is either failing or not receiving power.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • Printed Circuit Board (PCB)