Ideal boiler fault codes: what each one means
An Ideal Logic Combi2 shows a fault as F or L and a number on its display: F is a fault, L a lockout that the Restart button clears. The Logic Max Combi2 and Vogue Max Combi show the fault in words instead. The tables below give each fault's meaning and Ideal's stated action, from its own manuals.
Reviewed by Jordan Valentine-Dunn, Gas Safe registered engineer · Portsmouth Gas Heating · Last reviewed October 2026
Start with the gauge and the gas. Ideal's first low-pressure step on all three ranges is a reading of 1 to 1.5 bar; for an ignition fault, it is checking other gas appliances work and, on a prepayment meter, that there is credit.
Where does an Ideal boiler show its fault?
| Range | How the fault shows | Restart, in Ideal's words |
|---|---|---|
| Logic Combi2 | F or L and a number on the boiler status display, such as F01 or L02. | If an L code is shown, press the Restart button. The boiler repeats its ignition sequence. |
| Logic Max Combi2 | A text message, such as Ignition Lockout, with steps beneath it. Fault History and Fault Help sit in the menu. | To restart the boiler, press the Restart button. |
| Vogue Max Combi | A text message, such as LOW WATER PRESSURE. Fault History and Fault Help sit in the menu. | Press RESTART on the control panel. The boiler repeats its ignition sequence. |
What is the difference between an F code and an L code?
On the Logic Combi2, F means the boiler has a fault for a specific error and L means it is in lockout for a specific error; the number names the error. Ideal says the Restart button clears an L code. Several faults appear as either, such as F04 or L04 for the flow thermistor.
What do the Ideal Logic Combi2 fault codes mean?
| Code | Meaning (Ideal's words) | Manufacturer's stated action |
|---|---|---|
| F01 | Low Water Pressure | Check the gauge reads 1 to 1.5 bar and re-pressurise. If it still fails, call Ideal (in warranty) or an engineer. |
| F02 | Flame Loss | Check other gas appliances work. If not, check the gas is on at the meter and a prepayment meter has credit. |
| F04 or L04 | Flow Thermistor | Restart; if it fails, call Ideal or an engineer. |
| F07 | Low Mains Voltage | Contact a qualified electrician or your electricity provider. |
| F09 or L09 | Unconfigured PCB | Unconfigured or faulty PCB, or gas valve short circuit: call Ideal or an engineer. |
| L01 | Flow Temperature Overheat or No Water Flow | Check the gauge reads 1 to 1.5 bar and re-pressurise; if it fails, call Ideal or an engineer. |
| L02 | Ignition Lockout | Check the condensate pipe for blockages, then other gas appliances, the meter and prepayment credit. |
| L0C | 5 Boiler Resets in 15 minutes | Turn the electrical supply to the boiler off and on. |
| L0d | Blocked Flue/Condensate | Check the condensate pipe for blockages, then the gas supply as for L02. |
| F0U | Flow/Return Differential greater than 50°C | Call Ideal or an engineer. |
| L16 | Gas Valve Fault | Press the reset button for 1 to 3 seconds; if it fails, call Ideal or an engineer. |
| dU | Diverter Valve in mid-position for service | Rotate all knobs fully clockwise, turn the power off and on, then press Restart. |
The engineer's menu in section 4.1 adds F10 (spark generator fault), F12 (pump rotor blocked: clear the blockage), F13, F15 or F17 (pump fault), F14 (high mains voltage) and F16 (gas valve fault).
What do the Logic Max Combi2 fault messages mean?
| Message | Manufacturer's stated action |
|---|---|
| Low Water Pressure | Fill and vent the system so the gauge reads 1 to 1.5 bar with all valves open; then check the water pressure switch connections, and replace the switch. |
| Ignition Lockout | Check other gas appliances work, restart, and contact the installer if it persists. Engineer checks: inlet above 18 mbar, about 24 V DC at the gas valve, electrodes, spark generator, condensate trap. |
| Overheat Lockout | Fill and vent with all valves open. Above a 30°C flow and return differential, check the pump turns freely; replace it if the differential stays above 20°C. |
| Flame Loss | Check inlet above 18 mbar, 24 V DC at the gas valve with the flame on, the electrodes, spark generator, and a blocked condensate pipe or flue. |
| Flame On Before Gas Valve On | Restart the boiler; if it does not work, replace the electrode. |
| Fan Fault | Check the fan wiring to the PCB. With 230 VAC at the fan, replace the fan; without it, replace the PCB. |
What do the Vogue Max Combi fault messages mean?
| Message | Manufacturer's stated action |
|---|---|
| Low Water Pressure | With the boiler off and the system cold, fill to 1.0 to 1.5 bar, bleed the radiators, then refill. If the pressure loss recurs, contact the installer. |
| Ignition Lockout | Check other gas appliances work and a prepayment meter has credit, restart, and contact the installer if it persists. |
| Overheat Lockout | Fill and vent with all valves open. Above a 30°C differential, check the pump rotates freely and replace it if not below 20°C. |
| Too Many Resets | 5 restarts within 15 minutes: turn the power off and on. |
| Low Mains Voltage | Under 185 V: contact the electricity provider; if the voltage is OK, replace the pump, then the primary PCB. |
| Pump Rotor Blocked | Unblock the pump. |
| Flow/Return Reversed | Check the flow thermistor is correctly clipped to the pipe; replace the flow thermistor. |
Why does Ideal's website list different codes?
Ideal's fault codes page names no range and differs from the Logic Combi2 manual. It gives L5 as reset too many times in 15 minutes, where the Combi2 shows L0C and uses L05 for the return thermistor, and it adds L3 for no water flow and BCC chip C codes. Use the manual for the boiler fitted, found from its data plate.
How do you read an Ideal fault on the job? Two examples
A Logic Combi2 gurgles, then locks out with L02. Ideal's user guide says a blocked condensate pipe gurgles before an L02 lockout, so that pipe is the first check, and a frozen one is never thawed above ground level.
A Vogue Max shows LOW WATER PRESSURE, gauge under 1 bar. Ideal's steps: fill the cold system to 1.0 to 1.5 bar, bleed the radiators, refill, and call the installer if the loss returns.
When should you stop restarting and call an engineer?
When the fault returns after a restart. Ideal's Logic Combi2 steps end: if it still fails, call Ideal while under warranty, or a Gas Safe registered engineer after that.
A fault code is the manufacturer's diagnostic starting point, not a repair. Only a Gas Safe registered engineer may open the appliance: regulation 3 of the Gas Safety (Installation and Use) Regulations 1998 limits gas work to an HSE-approved class of persons. If you smell gas, restart nothing and call the National Gas Emergency Service on 0800 111 999.
For engineers, Manifold's fault codes library records each code seen on your team's checks against the appliance, and its manuals lookup finds Ideal's documentation by GC number.
Read next
Frequently asked
Sources
- Ideal Heating, Logic Combi2 C24, C30, C35 installation and servicing manual (UIN 237664 A08)
- Ideal Heating, Logic Max Combi2 C24, C30, C35 installation and servicing manual (UIN 237660 A05)
- Ideal Heating, Vogue Max Combi 26, 32, 40 installation and servicing manual (UIN 222378 A08)
- Ideal Heating, What does my fault code mean?
- Legislation.gov.uk, Gas Safety (Installation and Use) Regulations 1998, regulation 3
- National Gas, emergency contacts
Related guides
Last reviewed October 2026. This guide is general information, not legal or safety advice, gas safety work must be carried out by an appropriately Gas Safe registered engineer. Rules can change, so check the linked official sources for the current position.