Ideal Mexico Super 100FF / 125FF Fault codes & diagnostics

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

Regular Natural Gas 29.3-36.6 kW 1997-2005 Discontinued
GC Numbers 41-392-1241-392-13

Replaced by: Mexico HE

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Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
2 Emergency 32 High 2 Low

All 36 documented codes

Tap any card for details

49

Your boiler is failing to start up because the small ignition flame is not lighting properly.

High Engineer only £120-250

Parts commonly replaced

  • Thermocouple
  • Pilot Injector
  • Gas Valve
  • Ignition Lead
50

Your boiler is failing to keep its small starter flame lit, which prevents the main heating system from firing up.

High Engineer only £120-£250

Parts commonly replaced

  • Thermocouple
  • Gas Control Valve
  • Overheat Thermostat
  • Pilot Injector
51

Your boiler's small pilot light has started, but the main burner is failing to ignite to provide heating and hot water.

High Engineer only £140-£280

Parts commonly replaced

  • Gas Valve
  • Pilot Injector
  • Ignition Lead
E01 372

Your boiler has failed to light because it cannot detect a flame, which means your heating and hot water have stopped working.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB
E01 373

Your boiler has failed to ignite or stay lit, meaning it cannot produce heat or hot water because it has detected a problem with the flame or gas supply.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB
  • Flame rectification probe
E01 374

Your boiler has failed to ignite the flame reliably and has automatically switched itself off as a safety precaution.

High Engineer only £180-350

Parts commonly replaced

  • Ignition lead
  • Ignition electrode
  • Gas valve
E01 490

Your boiler has failed to ignite or stay lit, meaning it cannot produce heat or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control PCB

Related codes

E01 505

Your boiler has failed to light because it cannot detect that a flame is present in the burner.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Flame rectification probe
  • Ignition lead
  • PCB

Related codes

E01 507

Your boiler is failing to light the burner because it cannot detect that gas is flowing or igniting correctly.

High Engineer only £250-450

Parts commonly replaced

  • Gas valve assembly
  • Ignition lead
  • Ignition electrode
E01-372

Your boiler has failed to ignite or stay lit, meaning your heating and hot water have stopped working.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB
Showing 11–20 of 36
E01-374

Your boiler has failed to ignite or stay lit, meaning it cannot produce heat or hot water because it has lost its flame signal.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB
E01-490

Your boiler has detected a failure to ignite or a persistent loss of flame, meaning it cannot start up to provide heat or hot water.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB
E01-505

Your boiler is failing to light its pilot flame, meaning it cannot start the main burner to provide you with heating or hot water.

High Engineer only £120-250

Parts commonly replaced

  • Pilot burner assembly
  • Pilot injector
  • Thermocouple

Related codes

H 1

Your boiler has detected a critical internal fault with its electronic control system that prevents it from firing up safely.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
H 4

Your boiler has detected a failure during the ignition sequence which prevents it from firing up safely.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB
H A

Your boiler has detected an internal communication error and has safely shut itself down to prevent further issues.

High Engineer only £150-350

Parts commonly replaced

  • Main printed circuit board (PCB)
  • Wiring harness
H E

Your boiler's electronic brain is experiencing a critical internal communication failure, meaning the unit cannot safely operate.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

H F

Your boiler has detected a critical internal fault that prevents it from operating and requires a qualified engineer to inspect the internal control systems.

High Engineer only £150-300

Parts commonly replaced

  • PCB
  • Wiring harness
  • Control board
H n

Your boiler has detected an internal issue with its electronic control system and requires a professional to evaluate the main circuit board.

High Engineer only £180-350

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

H......F........

Your boiler has detected an electrical fault in the system responsible for monitoring the gas flame, meaning it will not start to ensure your home remains safe.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Flame rectification electrode
  • Wiring harness

Related codes

Showing 21–30 of 36
H......n........

Your boiler is failing to start because the electrical supply wires have been connected in the wrong order.

High Engineer only £90-160

Parts commonly replaced

  • Main PCB
  • Wiring harness
H.....1.....

Your boiler has lost the ability to accurately measure the temperature of the water flowing through it, so it has shut down as a precaution to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • Flow thermistor sensor
  • Wiring harness
H.....4......

Your boiler has detected an issue with the sensor that monitors the temperature of the exhaust gases, and it has shut itself down to keep your home safe.

High Engineer only £150-250

Parts commonly replaced

  • Flue overheat thermostat
  • Wiring harness

Related codes

H9

Your boiler has detected an internal fault within its electronic control system that requires a professional to investigate and reset.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
H9/L9

Your boiler has detected that the exhaust gases are becoming dangerously hot and has shut itself down to prevent damage or safety issues.

Emergency Engineer only £150-300

Parts commonly replaced

  • Flue overheat thermostat
  • Heat exchanger
  • Pump

Related codes

L 8

Your boiler has detected a critical internal error that prevents it from starting, which typically requires a qualified gas engineer to inspect the control systems and electrical connections.

High Engineer only £120-250

Parts commonly replaced

  • PCB (Printed Circuit Board)
  • Wiring harness
  • Control module
L A

Your boiler has detected a failure to ignite or a loss of flame during operation, and it has safely locked itself out to prevent gas buildup.

High Engineer only £120-250

Parts commonly replaced

  • Ignition lead
  • Spark electrode
  • Gas valve
  • PCB

Related codes

L E

Your boiler's electronic brain is experiencing an internal communication error and has safely shut itself down to prevent unpredictable operation.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

L F

Your boiler has failed to ignite the gas flame after three attempts and has locked itself out for safety reasons.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Spark generator

Related codes

L.......A........

Your boiler has detected that it is running too hot and has automatically switched itself off to prevent potential damage or overheating.

High Engineer only £150-300

Parts commonly replaced

  • Overheat thermostat
  • Pump
  • PCB
Showing 31–36 of 36
L.....E...... or H.....E......

Your boiler's electronic brain has encountered a software or communication error and requires a professional reset or component replacement to function safely.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
L....8.....

Your boiler has detected that the internal mechanism responsible for safely clearing exhaust gases is not operating correctly, so it has shut down to keep your home safe.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Printed circuit board

Related codes

L9

The boiler has detected a fault with the fan or the air pressure system, meaning it cannot push out waste gases safely and has shut down to prevent risk.

Emergency Engineer only £150-300

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Flue sampling points
LA/HA

Your boiler has become too hot and has automatically switched itself off to stay safe, so you will have no heating or hot water until the internal temperature drops.

High Engineer only £150-300

Parts commonly replaced

  • Overheat thermostat
  • Pump
  • PCB
Neon I3

Your boiler is receiving electrical power, and this light is simply a normal indicator that the mains switch is turned on.

Low DIY-safe

What to check first

  1. No action is required as this is a status light, not a fault code.
  2. If the boiler is not working despite the light being on, check that the thermostat is turned up.
  3. Ensure the programmer is set to 'On' or 'Auto'.
Neon SG1

This light simply shows that your boiler is currently trying to light its flame, which is a normal part of its startup sequence.

Low DIY-safe

What to check first

  1. No action is usually required as this is a status indicator rather than a fault.
  2. If the light flashes continuously without the boiler firing up, try turning the thermostat up.
  3. Check that your gas supply is turned on at the meter.