Main Combi 28 Fault codes & diagnostics

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

Combi Natural Gas 28 kW 2007-2008 Discontinued
GC Numbers 47-075-3047-075-2947-075-2847-075-27

Replaced by: Main Eco Compact

Download the Main Combi 28 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

This boiler uses indicator light combinations

Note which lights are on, off, or flashing and at what speed. Match the combination to the cards below. Do not reset until you have noted the pattern. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 11 High 1 Medium

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
47-075-30 Platinum Combi 40 HE 2007–2008
47-075-29 Platinum Combi 33 HE 2007–2008
47-075-28 Platinum Combi 28 HE 2007–2008
47-075-27 Platinum Combi 24 HE 2007–2008

All 13 documented codes

Tap any card for details

E20

Your boiler has lost the ability to accurately measure the temperature of the water circulating through your radiators, so it has shut down to protect the system.

High Engineer only £120-220

Parts commonly replaced

  • Central Heating NTC Sensor
  • Wiring Harness

Related codes

E28

Your boiler has detected a communication issue with the sensor that monitors the temperature of the gases leaving your flue, causing it to stop working to ensure your safety.

High Engineer only £120-200

Parts commonly replaced

  • Flue NTC Sensor
  • Wiring Harness

Related codes

E50

Your boiler is struggling to accurately measure the temperature of the water used for your taps, causing it to stop heating your hot water.

Medium Engineer only £120-180

Parts commonly replaced

  • Domestic Hot Water NTC Sensor

Related codes

E110

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

High Engineer only £120-250

Parts commonly replaced

  • Pump
  • Diverter Valve
  • Primary Heat Exchanger
  • NTC Sensor

Related codes

E119

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

High DIY-safe £80-120

What to check first

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

Parts commonly replaced

  • Pressure Relief Valve
  • Pressure Transducer
  • Expansion Vessel
E125

Your boiler has detected that water is not circulating correctly through the system, which is preventing it from heating your home or water safely.

High Engineer only £150-300

Parts commonly replaced

  • Central heating pump
  • Diverter valve
  • Flow sensor

Related codes

E130

Your boiler has detected that the gases being sent out through your chimney are getting too hot and has automatically shut down to keep your home safe.

Emergency Engineer only £150-£300

Parts commonly replaced

  • Flue Gas Sensor
  • Primary Heat Exchanger
  • Pump

Related codes

E133

Your boiler is failing to light because it cannot detect a flame or is not receiving a consistent supply of gas.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

E160

Your boiler has detected that the internal fan responsible for safely venting exhaust gases is not working correctly, causing the system to stop for safety reasons.

High Engineer only £150-300

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • Printed Circuit Board

Related codes

E193

Your boiler is failing to circulate water correctly before firing up, which prevents it from safely producing heat or hot water.

High Engineer only £150-300

Parts commonly replaced

  • Circulation pump
  • Pressure sensor
  • Main PCB

Related codes

Flame Failure

Your boiler has stopped working because it failed to light or lost its flame during operation, so it has turned itself off for safety.

High Engineer only £120-250

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Control PCB

Related codes

Overheat

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

High Engineer only £120-250

Parts commonly replaced

  • Pump
  • NTC Thermistor
  • Diverter Valve
  • Primary Heat Exchanger

Related codes

1 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.