Complete reference guide for all Ideal boiler fault codes. Find your error code below for detailed causes and step-by-step solutions. Ideal boilers include Logic, Logic+, Logic Max, Vogue, Mexico, and Isar ranges.
Listed below are all Ideal fault codes as described by the boiler manufacturer along with possible causes. Click “View Solution” for detailed step-by-step fixes, DIY tips, and when to call a Gas Safe engineer.
Ideal boilers use alphanumeric fault codes displayed on the digital screen:
– L codes indicate lockout faults requiring reset
– F codes indicate faults that may self-clear
– Status codes (C, D, 0) show normal operating modes
– Find your boiler model below and locate your fault code
| Fault Code | Description | Possible Cause | Solution |
|---|---|---|---|
| L1 | Flow temperature overheat or no water flow lockout | System circulation problem or pump failure | View Solution → |
| L2 | Ignition lockout | Gas supply issue or frozen condensate pipe | View Solution → |
| L5 / LC | Too many resets – 5 restarts within 15 minutes | Underlying fault causing repeated lockouts | View Solution → |
| L6 | False flame lockout | Flame detected before gas valve opens | View Solution → |
| F1 | Low water pressure | System pressure below 0.5 bar | View Solution → |
| F2 / FN / LN | Flame loss | Loss of flame during operation | View Solution → |
| F3 | Fan fault | Fan not operating or air pressure switch issue | View Solution → |
| F4 / L4 | Flow thermistor fault | Temperature sensor error or wiring issue | View Solution → |
| F5 / L5 | Return thermistor fault | Return temperature sensor error | View Solution → |
| F6 | Outside sensor fault | External temperature sensor failure | View Solution → |
| F7 | Low mains voltage | Less than 185V supply to boiler | View Solution → |
| F8 / L8 | PCB unconfigured or fault | Printed circuit board issue | View Solution → |
| F9 / L9 | PCB unconfigured or fault | Board needs configuring or replacing | View Solution → |
| FU | Temperature difference >50°C | Isolation valves may be closed | View Solution → |
| FA | Flow/Return reversed | Flow thermistor incorrectly positioned | View Solution → |
| FD | No water flow | Pump fault or system blockage | View Solution → |
| C0 | Boiler Chip Card (BCC) activation fault | BCC not properly inserted | View Solution → |
| C2 | Boiler Chip Card (BCC) fault | BCC needs replacing | View Solution → |
Note: These are NOT faults – they indicate normal boiler operation:
| Status Code | Meaning | Action Required |
|---|---|---|
| 0 | Standby mode – awaiting heating/hot water demand | No action – normal |
| C | Central heating call – target temperature reached | No action – normal |
| D | Hot water call – target temperature reached | No action – normal |
| c | Boiler firing in central heating mode | No action – normal |
| d | Boiler firing in hot water mode | No action – normal |
| F | Frost protection mode active | No action – normal |
| Fault Code | Description | Solution |
|---|---|---|
| L1 | Flow temperature overheat or no water flow lockout | View Solution → |
| L2 | Ignition lockout | View Solution → |
| LC | Turn power off and on (5 resets in 15 mins) | View Solution → |
| L6 | False flame lockout | View Solution → |
| F1 | Low water pressure | View Solution → |
| F2 / FN / LN | Flame loss | View Solution → |
| F3 | Fan fault | View Solution → |
| L4 / F4 | Control / no flow thermistor fault | View Solution → |
| L5 / F5 | Return thermistor fault | View Solution → |
| F6 | Outside sensor fault | View Solution → |
| F7 | Low mains voltage | View Solution → |
| F8 / L8 | PCB unconfigured or fault | View Solution → |
| F9 / L9 | PCB unconfigured or fault | View Solution → |
| FU | Temperature difference >50°C | View Solution → |
| Fault Code | Description | Solution |
|---|---|---|
| L1 | Flow temperature overheat or no water flow lockout | View Solution → |
| L2 | Ignition lockout | View Solution → |
| LC | 5 restarts within 15 minutes | View Solution → |
| L6 | False flame lockout | View Solution → |
| FA | Flow/Return reversed | View Solution → |
| FD | No water flow | View Solution → |
| F2 / FN / LN | Flame loss | View Solution → |
| F3 | Fan fault | View Solution → |
| L4 / F4 | Control / no flow thermistor fault | View Solution → |
| L5 / F5 | Return thermistor fault | View Solution → |
| F6 | Outside sensor fault | View Solution → |
| F7 | Low mains voltage | View Solution → |
| F8 / L8 | PCB unconfigured or fault | View Solution → |
| F9 / L9 | PCB unconfigured or fault | View Solution → |
| FU | Temperature difference >50°C | View Solution → |
| Fault | Description | Solution |
|---|---|---|
| Overheat lockout | System overheating – bleed radiators and check circulation | View Solution → |
| Ignition lockout | Check gas appliances work and restart boiler | View Solution → |
| Too many restarts | 5 starts within 15 minutes – turn power off and on | View Solution → |
| Flame on before gas on | False flame lockout | View Solution → |
| Water pressure | Fill system to 1.0 bar when cold, bleed radiators | View Solution → |
| Fault | Description | Solution |
|---|---|---|
| Too many resets | 5 restarts within 15 minutes | View Solution → |
| Flame on before gas valve | False flame detection | View Solution → |
| Flow thermistor fault | Flow temperature sensor error | View Solution → |
| Low mains voltage | Less than 185V – check supply or replace pump | View Solution → |
| Low water pressure | System pressure too low | View Solution → |
| Flow/Return reversed | Check flow thermistor clipped correctly | View Solution → |
| PCB recently replaced | Reset boiler after PCB replacement | View Solution → |
| Pump rotor blocked | Unblock pump rotor | View Solution → |
| Flow temp cannot reach 80°C | Check thermistors securely clamped | View Solution → |
| Overheat lockout | System overheating – call engineer | View Solution → |
| Ignition lockout | Ignition failure | View Solution → |
| Flame loss | Loss of flame during operation | View Solution → |
| Thermal fuse lockout | Safety thermal fuse has operated | View Solution → |
| Outside sensor fault | External sensor error | View Solution → |
| Return thermistor fault | Return sensor error | View Solution → |
| Fan fault | Fan or air pressure switch issue | View Solution → |
| PCB error | Printed circuit board fault | View Solution → |
| No CH but DHW working | Central heating issue – diverter valve | View Solution → |
| No DHW but CH working | Hot water issue – diverter valve | View Solution → |
| No water flow fault | Pump or circulation problem | View Solution → |
The most common Ideal fault. Easy DIY fix - simply repressurise your heating system to 1.0-1.5 bar using the filling loop.
Very common in winter months. Usually caused by frozen condensate pipe, gas supply issue, or electrode fault.
Fan not reaching correct speed or air pressure switch issue. Requires Gas Safe engineer with diagnostic equipment.
If your Ideal boiler is showing L2 during cold weather, your condensate pipe is very likely frozen. This white or grey plastic pipe runs from your boiler to an outside drain and can freeze solid in temperatures below 0°C.
Quick DIY Fix:
1. Locate the condensate pipe outside (21-32mm plastic pipe)
2. Pour warm (NOT boiling) water slowly along the full length
3. You’ll hear gurgling sounds when the blockage clears
4. Reset your boiler and it should fire up
Long-term Prevention:
Have the pipe insulated by a Gas Safe engineer. Proper insulation costs £50-100 and prevents future freezing, saving you emergency callout fees.
**Still showing L2?** Call us: 01304 381999
✅ F1 – Low Pressure
– Turn off boiler
– Locate filling loop (under boiler)
– Open both valves slowly
– Watch pressure gauge reach 1.0-1.5 bar
– Close both valves
– Turn boiler back on
✅ L2 – Frozen Condensate (Winter)
– Pour warm water on external pipe
– Wait for gurgling sounds
– Reset boiler
– Consider insulation
✅ LC / L5 – Too Many Resets
– Don’t keep resetting
– Turn power off at wall switch
– Wait 2 minutes
– Turn power back on
– If fault returns, call engineer
✅ No Display
– Check power to boiler
– Check fuse in spur
– Check MCB in consumer unit
– Check boiler isolation switch
❌ NEVER Attempt DIY:
These require Gas Safe registered engineers with Ideal boiler training and diagnostic equipment.
✅ You CAN Try:
Low pressure (F1) – Repressurise system to 1.0-1.5 bar
Thaw frozen condensate pipe (L2 in winter)
Bleed radiators (for L1 overheat)
Reset boiler after power cut
Check power supply (no display)
Check gas supply is on (L2)
Ensure isolation valves are open (FU)
Turn power off and on (LC – too many resets)
Check all radiator valves are open
How to Reset Ideal Boiler:
Press and hold the reset button (flame symbol) for 2-3 seconds. For persistent faults, turn power off at wall, wait 2 minutes, turn back on.
Important: If the fault code returns within minutes, there’s an underlying problem. Don’t keep resetting – call a professional to diagnose the root cause.
Our Gas Safe registered engineers are Ideal boiler specialists serving Kent and surrounding areas. We service and repair all Ideal models including Logic, Logic+, Vogue, Mexico, and Isar ranges.
✓ Same-day emergency callouts available
✓ All major brands serviced and repaired
