Main Eco Elite Fault codes & diagnostics

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

Combi Natural Gas 24-28 kW 2013-2016 Discontinued

Replaced by: Main Eco Compact

Download the Main Eco Elite manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

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Severity at a glance

Each cell = one fault code. Hover to identify.
15 High 1 Medium 1 Low
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The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 17 documented codes

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110

Your boiler has switched itself off because it has gotten too hot, likely due to trapped air or a blockage stopping water from circulating properly.

High DIY-safe £100-280

What to check first

  1. Turn off the boiler and allow it to cool down completely.
  2. Use a radiator key to bleed all radiators and remove trapped air.
  3. Check the boiler pressure gauge and top it up to 1.5 bar if it has dropped.
  4. Press the 'Reset' button on the boiler control panel.

Parts commonly replaced

  • Circulation Pump
  • Overheat Thermostat
  • NTC Temperature Sensor

Related codes

Full explanation for 110
119

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

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (a flexible silver hose) underneath or near the boiler.
  2. Open the one or two small taps on the filling loop until you hear water entering the system.
  3. Watch the pressure gauge and close the taps once the needle reaches between 1.0 and 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure relief valve

Related codes

Full explanation for 119
125

Your boiler has detected that water is failing to move through the system correctly, which could be caused by air locks, a blockage, or a pump issue.

High DIY-safe £180-450

What to check first

  1. Check if your radiator valves are open
  2. Ensure the system pressure is between 1.0 and 1.5 bar
  3. Gently bleed your radiators to remove trapped air

Parts commonly replaced

  • Circulation pump
  • Flow temperature sensor
  • Automatic air vent

Related codes

Full explanation for 125
127

Your boiler has failed to heat the water to a high enough temperature to complete its automatic routine cleaning cycle that prevents bacteria growth.

Low DIY-safe £0-120

What to check first

  1. Check that your hot water temperature dial is set to its normal operating position, not at its lowest.
  2. Ensure the boiler has been left switched on consistently so it can complete its timed weekly heat cycle.
  3. Restart the boiler using the reset button to see if the cycle completes successfully on the next attempt.

Parts commonly replaced

  • No parts usually required
  • Hot water temperature sensor (NTC thermistor)
  • Diverter valve

Related codes

Full explanation for 127
133

Your boiler has tried to light several times but cannot create a steady flame, causing it to shut down for safety.

High DIY-safe £100-280

What to check first

  1. Check that your gas pre-payment meter (if applicable) has credit.
  2. Ensure your external gas emergency control valve is in the 'on' position.
  3. Hold the selector switch to 'R' for five seconds to attempt a reset.
  4. If it is freezing outside, check that your white plastic condensate pipe hasn't frozen.

Parts commonly replaced

  • Spark electrode
  • Gas valve
  • Ignition lead
  • PCB

Related codes

Full explanation for 133
160

Your boiler has stopped working because the internal fan, which safely pushes exhaust gases out of the flue, is not running at the correct speed.

High Engineer only £220-£450

Parts commonly replaced

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

Related codes

Full explanation for 160
E1

Your boiler has become too hot and has shut down as a safety precaution to prevent damage.

High DIY-safe £100-250

What to check first

  1. Turn off the boiler and allow it to cool down completely.
  2. Breathe any trapped air out of your radiators using a radiator key.
  3. Check the boiler pressure gauge and top it up to 1.5 bar if it has dropped.
  4. Reset the boiler by turning the selector switch to 'R' for at least five seconds.

Parts commonly replaced

  • Overheat Thermostat
  • Circulating Pump
  • NTC Thermistor

Related codes

Full explanation for E1
E2

Your boiler is struggling to push water around your radiators, usually because of trapped air or a blockage.

High DIY-safe £80-250

What to check first

  1. Turn off your heating and allow the radiators to cool down.
  2. Use a radiator key to bleed all radiators, starting from the lowest floor.
  3. Check your boiler pressure gauge and use the filling loop to top it up to 1.5 bar if it has dropped.

Parts commonly replaced

  • Circulation Pump
  • Auto Air Vent
  • Main Heat Exchanger (if scaled)

Related codes

Full explanation for E2
E3

Your boiler's electronic control centre has developed an internal error and can no longer safely operate the system.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
Full explanation for E3
E20

Your boiler has lost its connection to the sensor that measures the temperature of the water for your radiators, meaning it cannot heat your home safely.

High Engineer only £90-160

Parts commonly replaced

  • Central Heating (Flow) NTC Thermistor
  • Connecting wiring harness

Related codes

Full explanation for E20
E28

Your boiler's computer system is currently reporting that it is not compatible with the specific version of the internal control board installed, meaning it cannot safely operate your heating or hot water.

High Engineer only £250-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Full explanation for E28
E50

Your boiler has detected a problem with the sensor that measures hot water temperature, which means it may not be able to heat your taps correctly.

Medium Engineer only £90-160

Parts commonly replaced

  • Hot water NTC thermistor
  • Connecting wiring harness

Related codes

Full explanation for E50
E110

Your boiler has likely overheated, causing a safety sensor to shut the system down to prevent damage.

High DIY-safe £100-280

What to check first

  1. Wait 30 minutes for the boiler to cool down fully.
  2. Check that your radiator valves are open and not blocked by furniture.
  3. Check the boiler pressure gauge and top it up to 1.5 bar if it is too low.
  4. Turn the selector switch to the 'R' (Reset) position for at least five seconds and then release it.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Water Pressure Sensor

Related codes

Full explanation for E110
E119

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

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually two silver braided hoses under the boiler)
  2. Open the valves slowly until you hear water entering the system
  3. Watch the pressure gauge and close the valves once it reaches between 1.0 and 1.5 bar

Parts commonly replaced

  • Filling loop
  • Water pressure switch
  • Expansion vessel

Related codes

Full explanation for E119
E125

Your boiler has detected that water is not moving through the system properly, which is causing it to overheat and shut down for safety.

High Engineer only £180-£450

Parts commonly replaced

  • Circulation pump
  • Diverter valve motor
  • Main heat exchanger (flushing)

Related codes

Full explanation for E125
E133

Your boiler has tried to ignite but cannot get a steady gas supply or sense a flame, which means it has locked itself out for safety.

High DIY-safe £100-£250

What to check first

  1. Check if your gas meter has credit (if on a prepayment meter)
  2. Check if other gas appliances, like a hob, are working to confirm gas supply
  3. Rotate the selector switch to the 'R' (Reset) position for five seconds and release
  4. If it is freezing outside, check if your white plastic condensate pipe is frozen and thaw it with warm water

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for E133
E160

Your boiler has detected a problem with the fan that clears exhaust gases, preventing it from starting up safely.

High Engineer only £180-£400

Parts commonly replaced

  • Extraction Fan
  • Fan Wiring Harness
  • Printed Circuit Board (PCB)

Related codes

Full explanation for E160