Ideal Mexico HE Fault codes & diagnostics

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

Regular Natural Gas 15-36 kW 2005-2013 Discontinued
GC Numbers 41-409-1141-409-1241-409-1341-409-1441-409-1541-409-16

Replaced by: Mexico HE (2013-present) or Mexico Linea

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2 Emergency 33 High

All 35 documented codes

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78

Your boiler has detected a communication issue with the sensor that monitors the temperature of the exhaust fumes, causing it to shut down for safety reasons.

High Engineer only £150-250

Parts commonly replaced

  • Flue thermistor sensor
  • Wiring harness
  • PCB

Related codes

79

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

High Engineer only £100-180

Parts commonly replaced

  • Main PCB

Related codes

Automatic Shutdown

Your boiler has switched off because water produced during the heating process cannot drain away properly, likely due to a blockage in the pipe leading outside.

High Engineer only £90-180

Parts commonly replaced

  • Condensate trap
  • Condensate pipework
ERROR CODE 1

Your boiler has stopped working for safety reasons and needs to be manually reset to try and get it running again.

High Engineer only £100-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed circuit board
ERROR CODE 2

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

  • High limit thermostat
  • Pressure switch
  • Pump
  • Heat exchanger
ERROR CODE 3

Your boiler has detected that the water flow or pressure is not moving correctly, which has caused it to turn off as a safety precaution.

High Engineer only £150-300

Parts commonly replaced

  • Water pressure switch
  • Pump
  • Pressure sensor
ERROR CODE 4

Your boiler is failing to clear combustion gases properly, which has triggered a safety shutdown to prevent unsafe operation.

High Engineer only £150-300

Parts commonly replaced

  • Air Pressure Switch (APS)
  • Fan Assembly
  • Venturi
  • Flue seals

Related codes

ERROR CODE 5

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

High Engineer only £120-180

Parts commonly replaced

  • Central Heating NTC Sensor

Related codes

ERROR CODE 6

Your boiler is experiencing a communication error with the temperature sensor used for your hot water, which means it cannot accurately detect or manage the water temperature.

High Engineer only £120-200

Parts commonly replaced

  • DHW Thermistor
  • Wiring Harness
ERROR CODE 7

Your boiler has detected that the flue exhaust is becoming dangerously hot and has shut itself down to prevent damage or fire risk.

Emergency Engineer only £150-300

Parts commonly replaced

  • Flue thermostat
  • Heat exchanger
  • Primary flow sensor
Showing 11–20 of 35
ERROR CODE 8

Your boiler has detected that the pipe used to drain away water produced during heating is blocked, which is forcing the system to shut down for safety.

High Engineer only £90-180

Parts commonly replaced

  • Condensate trap
  • Condensate pipework
H......F........

Your boiler has detected a flame when there shouldn't be one, or there is an electrical fault with the sensor that tracks the flame.

High Engineer only £120-£280

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Printed Circuit Board (PCB)
H......n........

Your boiler has detected that the electrical wiring coming into the unit is connected incorrectly, meaning the live and neutral wires are swapped.

High Engineer only £80-160

Parts commonly replaced

  • Main PCB
  • External Wiring Connections
H.....4......

Your boiler has detected that a safety sensor in the flue pipe is reporting an incorrect temperature reading.

High Engineer only £120-190

Parts commonly replaced

  • Flue thermistor
  • Wiring harness
H1

Your boiler has stopped working because it cannot properly measure the temperature of the water leaving the unit.

High Engineer only £90-160

Parts commonly replaced

  • Flow thermistor (NTC sensor)
  • Wiring harness
  • Main PCB
H4

Your boiler has detected an issue with the sensor that monitors the temperature of the exhaust gases, causing the system to shut down as a safety precaution.

High Engineer only £120-190

Parts commonly replaced

  • Flue Thermistor
  • Wiring Harness

Related codes

H9

Your boiler has sensed that the exhaust gases are getting too hot and has shut down as a safety precaution to prevent internal damage.

High Engineer only £120-400

Parts commonly replaced

  • Heat Exchanger (Cleaning/Descaling)
  • Flue Thermistor
  • Main PCB

Related codes

H9/L9

Your boiler has detected that the gases venting out of your home are getting too hot, so it has safely shut itself down to prevent damage or safety issues.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue gas overheat sensor
  • Heat exchanger
  • Pump

Related codes

HA

Your boiler has detected that the water inside is getting too hot and has shut itself down as a safety precaution.

High DIY-safe £120-300

What to check first

  1. Check that your radiator valves are open and not turned to zero.
  2. Verify that the system water pressure is between 1 and 1.5 bar on the gauge.
  3. Allow the boiler to cool down for 20 minutes and press the Reset button.

Parts commonly replaced

  • Circulation Pump
  • Overheat Thermostat
  • Thermistor

Related codes

HE

Your boiler's internal computer has encountered a critical electronic failure and can no longer control the heating process safely.

High Engineer only £280-£450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Showing 21–30 of 35
HF

Your boiler has detected a problem with the sensor that tracks the flame, meaning it cannot safely confirm if the gas is ignited and has shut down as a precaution.

High Engineer only £120-£280

Parts commonly replaced

  • Flame Sensing Electrode
  • Ignition Lead
  • Printed Circuit Board (PCB)
HHHHH:::::AAAAA

Your boiler has stopped functioning entirely and is failing to provide both heating and hot water to your home.

High Engineer only £150-350

Parts commonly replaced

  • Printed Circuit Board
  • Ignition Lead
  • Fan Assembly

Related codes

Hn

Your boiler has detected that the electrical wiring is connected the wrong way around, or there is a fault with the electronics that makes it think so.

High Engineer only £100-£250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Mains wiring harness

Related codes

Ignition Lockout

Your boiler has failed to start up because it isn't receiving the gas it needs to create a flame.

High Engineer only £120-250

Parts commonly replaced

  • Ignition Lead
  • Ignition Electrode
  • Gas Valve
  • PCB

Related codes

L-A

Your boiler has become too hot and has automatically shut itself down to prevent damage and ensure safety.

High DIY-safe £120-280

What to check first

  1. Check that your radiator valves are open
  2. Ensure there is enough water pressure in the system (usually between 1 and 1.5 bar on the gauge)
  3. Once the boiler has cooled down, press the reset button on the front control panel

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Thermistor
L-F

Your boiler has failed to light or maintain a flame, meaning your heating and hot water have stopped working.

High DIY-safe £120-350

What to check first

  1. Check if other gas appliances, like a hob, are working to ensure gas is reaching your home
  2. Check if your gas meter has credit
  3. Press the 'Reset' button on the boiler control panel

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Ionisation Lead
  • Ignition PCB
L8

Your boiler has stopped working because the fan inside, which helps safely push waste gases out of your home, is not spinning correctly.

High Engineer only £280-£450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness
L9

Your boiler has shut down because the internal gases have reached a temperature that is dangerously high for the system.

High Engineer only £150-£450

Parts commonly replaced

  • Main Heat Exchanger
  • Flue Thermistor
  • Pump

Related codes

LA

Your boiler has become too hot and has shut itself down for safety purposes.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open to allow water to circulate.
  2. Ensure your system water pressure is between 1 and 1.5 bar on the gauge.
  3. Allow the boiler to cool down and press the reset button on the control panel.

Parts commonly replaced

  • Circulation pump
  • Overheat thermostat
  • Heat exchanger (flushing/cleaning)

Related codes

LE

Your boiler’s internal computer has encountered a critical error and cannot communicate properly with the system.

High Engineer only £280-£450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Showing 31–35 of 35
LF

Your boiler has tried to ignite three times but failed to stay alight, so it has shut down for safety.

High DIY-safe £100-280

What to check first

  1. Check if your gas supply is active (e.g., check other gas appliances or your meter credit)
  2. Locate the reset button (marked 'C') and press it once to restart the ignition sequence
  3. Check if the condensate pipe (outside white plastic pipe) is frozen if the weather is very cold

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Probe
  • Gas Valve
  • PCB
LLLLL ::::: FFFFF

Your boiler is trying to start but keeps failing, which means it cannot provide heat or hot water.

High Engineer only £150-300

Parts commonly replaced

  • Ignition lead
  • Ignition electrode
  • Gas valve
LLLLL:::::AAAAA

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

High Engineer only £120-250

Parts commonly replaced

  • Overheat thermostat
  • Pump
  • Diverter valve
  • Heat exchanger

Related codes

Overheat condition

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

High Engineer only £150-300

Parts commonly replaced

  • Overheat thermostat
  • Pump
  • Primary heat exchanger
  • PCB
Red operational light 2 (E)

Your boiler has failed to start its burner multiple times and has safely shut itself down to prevent a gas build-up.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB (Printed Circuit Board)

Related codes